Sacrococcygeal Teratoma Sacrococcygeal teratoma (SCT) is a tumor that arises from the tip of the tailbone called the coccyx. An SCT develops from embryonic stem cells in the primitive streak at the tail end of the developing embryo. The primitive streak normally completely disappears by the fourth week of pregnancy. If stem cells in the primitive streak persist beyond the fourth week of embryonic development they will give rise to an SCT. What is sacrococcygeal teratoma (SCT)?SCT is a germ cell tumor which can give rise to all 3 layers of the embryo. That is why teratomas have many structures within them such as hair teeth fat neural tissue in a disorganized mass. SCTs can grow quite large during fetal development and have up to a 50% mortality when diagnosed prenatally. In contrast, SCTs diagnosed at birth have only a 5% mortality. Fetal SCTs not only grow quite large but become extremely vascular and can cause congestive heart failure in the baby. The high cardiac output results in polyhydramnios (too much amniotic fluid) which is in turn leads to preterm labor, placentomegaly (enlarged placenta) and hydrops (end-stage heart failure with fluid collections in the chest and abdomen). SCT is also one of those rare fetal conditions which can make the mother sick. SCT puts the mother at increased risk for preeclampsia which is characterized by increased blood pressure (>140/90) and increased protein in the urine (proteinuria >300 mg/24 hour urine specimen). The most severe end of the spectrum is maternal “mirror” syndrome in which the mother’s condition mirrors the illness in the baby with massive swelling, high blood pressure, and pulmonary edema. If not delivered urgently, mirror syndrome can be fatal for the mother. Another condition in the spectrum of maternal illness caused by SCT, is the development of the HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets) which can also be lifethreatening. SCT diagnosed in utero has a broad range of outcomes depending upon the size and nature of the SCT. The most common are type I and type II SCTs which are completely external (type I) and those that are external but extend into the fetal pelvis (type II). Types I and I SCTs account for 80% of fetal SCTs. The SCT can vary in how much is cystic and how much is solid. Predominantly cystic SCTs are not as dangerous and do not develop the vascularity that results in high-output heart failure, hydrops and death. There are prognostic measurements which help define the risks for complications in SCT. These measurements include the tumor volume index (TFR), which is a ratio of the tumor volume of the SCT to the estimated fetal weight, the tumor volume to fetal head volume ratio (STV/HV ratio), and the solid tumor volume to estimated fetal weight ration (STVI). Prognostic information can be obtained by ultrasound measurement of the tumor volume to fetal weight ratio (DFR) this is performed by measuring the greatest dimension of the SVTs length width and height using the formula for appropriate ellipse (L times W times H x0.5 to) to estimate tumor volume then dividing by the estimated fetal weight. A TFR of greater than 0.95 suggestive poor prognosis a TFR of greater than 0.12 is associated with both a poor fetal prognosis but also maternal complications. Another prognostic measurement in SCT is the tumor volume to head volume ratio (S TV/Hb) which is the ratio of the volume of the SCT to the volume of the fetal head. And ST V/HV ratio of less than 1.0 is associated with fetal survival while NST VE/HV ratio of greater than 1.0 is associated with a 61% fetal mortality. Fetal MRI can also be used to define the solid and cystic components of the SVT. While total SCD SET tumor volume to estimated fetal weight ratio (TV/EFW ratio) provides overall risk stratification solid tumor volume to estimated fetal weight or STD/EFW ratio is a better predictor of adverse fetal outcome. At this TVI of greater than 0.09 correlated with 120 fold increase in risk of developing high-output cardiac state or hydrops. SCTs are most often benign tumors but do have malignant potential. The SCT produces alpha-fetoprotein which is a useful biomarker that should progressively fall during the first year of life. If the alpha-fetoprotein increases it should trigger a search for persistent or recurrent SCT or malignant transformation into a yolk sac tumor. Both of these types of recurrences require surgical excision, and in the case of yolk sac tumor, chemotherapy in addition. How common is has SCT?SCT is one of the most common tumors in newborns but is still quite rare occurring in only 1 and 23,000 to 40,000 live births. SCT is 4 times more common in females than males. A malignant SCT however, is more common in males. How is an SCT diagnosed?The diagnosis of SCT is typically made on routine prenatal ultrasound. SCT is a disorganized mass with solid and cystic components arising from the fetal coccyx presenting as a large heterogeneous mass on the baby’s bottom. The ultrasound may or may not show extension into the baby’s pelvis or abdomen. Ultrasound for SCT should also include signs of high-output cardiac output state such as polyhydramnios, dilated IVC, Doppler velocimetry abnormalities in the umbilical artery or ductus venosus, and signs of hydrops. If SCT is suspected on ultrasound, a fetal MRI is indicated to define the size of the tumor, extent of the internal component in the pelvis or abdomen, and if there is obstruction or compression of the rectum vagina or bladder outlet. SCTs can grow rapidly and the faster the SCT grows the greater the risk of high-output cardiac failure, polyhydramnios, hydrops, premature delivery, and death. Adverse outcomes in SCT were observed when growth of the SCT exceeded 61 cm³/week and increased risk of fetal demise when the growth exceeded 165 cm³/week. Color Doppler ultrasound can be used to characterize the vascularity of the SCT. Solid vascular SCTs are those at greatest risk for complications and fetal mortality. On Doppler velocimetry, waveforms of various fetal vessels can identify impending fetal heart failure. As the blood flow to the SCT increases the SCT may “steal” blood flow from the placenta as indicated by flow reversals in end diastolic flow in the umbilical artery. As blood flow through the SCT increases there is a short circuit through the tumor increasing blood return to the heart causing the IVC to dilate. As the heart strains to keep up the a wave in the ductus venosus may become reversed indicating functional deterioration of heart. It is also important to evaluate the middle cerebral artery peak systolic flow velocity (MCA-PSV) in all fetuses with an SCT. The MCA-PSV increases with both anemia and increased cardiac output. Hemorrhage into the tumor can cause anemia in the fetus which is reflected in the MCA-PSV waveform. The interpretation of an elevated MCA-PSV in a baby with SCT must be interpreted cautiously in combination with measuring the combined ventricular output. What is the prenatal natural history of SCT?The growth of fetal SCT is quite variable and as a result so is the prenatal natural history. In general, small SCTs (less than 7 cm in largest diameter) really get into trouble prenatally. However, several parameters should be followed as they may be early indicators of poor prognosis including: Tumor size, solid versus cystic componenets, rate of growth, degree of vascularity, signs of impaired heart function, and development of polyhydramnios. As the SCT grows it develops increasing vascularity with arteriovenous shunting within the SCT. The high cardiac output stimulates cardiac hypertrophy (thickening of the heart) and eventually cardiac decompensation, abnormal Doppler changes and hydrops. As part of ongoing sonographic and echocardiographic surveillance measurement of the IVC greater than 0.6 cm, combined ventricular output of greater than 600 mL/kg/min, and descending peak systolic aortic flow velocity of greater than 100 cm/s are indicative of a high cardiac output state and risk for developing hydrops and maternal mirror syndrome. How is pregnancy complicated by a CT managed?A pregnancy complicated by SCT requires close sonographic and fetal echocardiographic surveillance due to the risks of fetal complications of polyhydramnios, preterm labor, preterm delivery and hydrops and maternal risks of maternal mirror syndrome. Weekly ultrasound examinations should be performed to assess amniotic fluid index, tumor growth, Doppler changes and earliest signs of hydrops. Weekly fetal echocardiogram should be obtained to monitor combined ventricular output, descending aortic flow velocity, and signs of cardiac dysfunction. Evidence of the earliest signs of heart failure, placentomegaly, and/or hydrops should be sought as these may progress rapidly and may be harbingers of preterminal events. Patients should be advised of signs and symptoms of preterm labor and have limited activity and cervical checks on a routine basis. Prognostic variables such as weekly tumor growth, STVI, TFR, and STV/HV ratio should be measured. Maternal blood pressure and signs of peripheral edema should be assessed on each visit as met monitoring for maternal mirror syndrome. Depending upon the size and growth of the SCT, monitoring may need to be twice a week to be sure that progression does not precipitate cardiac decompensation and hydrops before fetal intervention can be considered. How is SCT treated in utero?Because perinatal mortality in SCT ranges from 25 to 37%, various forms of fetal surgery have been attempted to improve these outcomes. Death occurs primarily in the fetus with fast-growing solid and highly vascular tumors causing high-output cardiac failure, often exacerbated by hemorrhage into the SCT and anemia. There are no uniformly excepted criteria for fetal surgery, but intervention prior to the development of full-blown hydrops offers the best chances for survival. Which interventions are indicated depends on gestational age at which evidence of high-output cardiac state develops, Doppler abnormalities, and/or early signs of hydrops develop. If viability has been reached, early delivery and urgent resection either by EXIT-to-resection or after delivery is an option to avoid intrauterine demise. This approach is associated with survival approaching 50%. Adzick and Crombleholme performed the first successful open fetal surgery for resection of an SCT at 25 weeks gestation. This fetus had rapid enlargement of the a II SCT with polyhydramnios, placentomegaly, and maternal tachycardia and proteinuria suggesting early mirror syndrome. The external portion of the SCT was excised leaving the intrapelvic portion in place. This interrupted the arteriovenous communications within the tumor, normalized the combined ventricular output with resolution of hydrops and placentomegaly over the following 10 days. The baby was delivered by cesarean section at 29 weeks’. A small series of 4 patient’s underwent open fetal surgery are were successful. But one neonate died due to premature closure of the ductus arteriosus in utero. There were other cases of open fetal surgery performed at UCSF and Cincinnati Children’s but it was apparent that keeping mother pregnant after technically successful open fetal surgery was a significant challenge and prematurity was uniform in all of these cases. Because the primary cause of fetal mortality and morbidity in SCT is the vascularity of the tumor and arteriovenous shunting through the tumor, various attempts have been made to devascularize the SCT using minimally invasive techniques. The first of these was using radiofrequency ablation in which a specially designed needle device is placed under ultrasound guidance into the SCT to generate heat which clots off the vessels supplying the SCT. In a report of 4 patients treated by RFA two died due to bleeding and the other two fetuses delivered at 28 and 31 weeks’ gestation, respectively, both with evidence of extensive necrosis of pelvic and perineal structures. Tthe uncontrolled nature of the thermal energy used in RFA makes it unsuitable to devascularize SCT in a precise way. Interstitial laser photocoagulation has been reported in 9 hydropic SCTs. The rationale for this approach is that individual vessels can be targeted to devascularize the SCT with minimal injury to the adjacent tissues. This approach is meant to temporize, as the SCT will parasitize additional blood supply over time. In this small series, 2 developed PPROM and delivered prior to 32 weeks’ gestation. Fetal demise occurred in 4 and neonatal demise in 2 with an overall survival of 4 out of 10. Crombleholme has developed criteria for interstitial laser devascularization of SCT which include: 1) perform prior to the onset of hydrops; 2) presence of elevated combined ventricular output > 600 ml/kg/min; 3) only vessels in the exophytic portion of the SCT; 4) vessel must be surrounded by tissue to prevent rupture (no surface vessels); 5) arterial inflow vessels only. Early experience with interstitial laser suggests that it can reverse hydrops caused by high-output failure due to arteriovenous shunting through the tumor. This is a temporizing measure however, as recurrent high output state is likely to recur within 4 weeks. This may be sufficient time however, to significantly improve the baby’s survival and reduce complications associated with premature One of the most difficult aspects of fetal surgery for SCT is keeping the mother pregnant after successful resection. In some cases, fetal surgery is not an option due to preterm labor, maternal mirror syndrome, or cervical incompetence. We have pioneered the use of EXIT-to-resection for high risk SCTs. During the EXIT procedure the external portion of the SCT is removed using a surgical stapling device to interrupt the vascular connections causing the high output state. The residual pelvic SCT is removed when the baby reaches the equivalent of their due date (40 post-conceptual weeks). In Crombleholme’s series of 9 patient’s who underwent EXIT-to-Resection for high risk SCTs 8 of 9 have been long-term survivors. The only death occurred in 30-week gestation fetus unrelated to SCT. This baby was found during the EXIT procedure to have laryngotracheal hypoplasia in which the S-windpipe was too underdeveloped for even the smallest endotracheal tube or tracheostomy tube. How is SCT treated in the newborn?One of the most important aspects of caring for the fetus with SCT is gentle handling of the baby with SCT, which is prone to internal bleeding. The majority of SCTs are born prematurely and are at risk for all the complications associated with prematurity. Excellent venous access is important because of the risk of bleeding into the SVT. The baby, especially if premature, may need respiratory support. If there is a high output state and/or cardiac dysfunction echocardiogram will be help guide treatment with inotropic agents (to support cardiac function and blood pressure). If there is no high output state there may be no urgency to resect the SCT and attention should focus on the treatment of the respiratory insufficiency, anemia, and imaging studies to plan the resection. If the baby is in a high output state then surgery to partially resect the SCT and eliminate the cause of the high output high cardiac output state is urgent. As with open fetal surgery, there is no need to perform a complete resection, but the goal should be to eliminate the cause of the high output state. This can be accomplished with the use of a thick tissue surgical stapling device once the anal sphincter complex has been mobilized off the tumor. The timing of the resection of the residual SCT can be guided by the pathology of the resected tumor. In the absence of any malignant rests of tumor within the SCT, weeks to months of growth will facilitate subsequent resection of the intrapelvic portion of the tumor and the coccyx (to prevent tumor recurrence). If on pathology there is evidence of malignant yolk sac tumor then earlier complete resection would be advisable In cases in which the SCT is quite vascular the risk of massive hemorrhage during surgery can be mitigated by placing a Rommel tourniquet around the distal aorta prior to resecting the SCT. If excessive bleeding is encountered this tourniquet allows control of the arterial inflow while the source of bleeding is controlled. What are the long-term outcomes of SCT?SCT is usually a benign tumor but with the potential for malignant transformation. All babies with SCT should be followed for a minimum of 3 years before being declared disease-free. Alpha-fetoprotein level should be monitored every 3 months looking for signs of recurrence. If there are microscopic rests of malignant cells on the pathology of the SCT then the alpha-fetoprotein should be checked every 6 weeks. In addition physical examination with rectal examination and abdominal pelvic MRI should be performed every 6 months for the first year and then yearly until year 3. Recurrences, if they occur usually present in the first year after resection. Urologic complications are underappreciated sequelae of the mass-effect of the SCT and the surgical resection. We showed that type II and type III SVTs had urologic complications in 60% of cases. In addition, 46% of SCTs on long-term follow-up have impaired bowel function including constipation and incontinence. What is the risk of recurrence of SCT?Most cases of SCT are sporadic with negligible rates of recurrence in subsequent pregnancies at less than 1%. There are familial cases of SCT with a suggestion of autosomal dominant inheritance, and so a 50% recurrence risk. Familial SCT is almost always presacral in location and can present as part of Currarino’s triad is (presacral tumor, anorectal malformation, and sacral anomaly). For Medical Professionals Sacrococcygeal teratoma (SCT) is defined as a neoplasm composed of tissues from either all three germ layers or multiple foreign tissues lacking an organ specificity arising in the sacrococcygeal region (Gross et al., 1951; Mahour et al., 1975). BackgroundBecause of the multiple cell lineages that characterize these tumors, it was previously suggested that SCT was of germ cell origin or a form of fetus in fetu (Theiss et al., 1960; Linder et al., 1975). Early theories suggested a “twinning accident” with incomplete separation during embryogenesis and abnormal development of one fetus (Waldhausen et al., 1963; Ashley, 1973; Cousins et al., 1980). In support of this theory, several authors have noted a family history of twinning in many SCT patients (Hickey and Layton, 1954; Grosfeld et al., 1976; Gross et al., 1987). However, more recently, SCT has been thought to arise from a totipotent somatic cell originating in Hensen’s node (Gross et al., 1987). SCTs develop at the base of the coccyx from residual cells from the embryonic primitive streak or Henson’s node. The primitive streak is made up of totipotential cells and helps determine the cranial/caudal and left/right axes of the embryo. The primitive streak forms at the beginning of the third embryonic week and regresses by the fourth week. This node is a caudal cell mass in the embryo that appears to escape normal inductive influences (Bale, 1984). If totipotential cells of the primitive streak persist beyond the fourth week, they may give rise to an SCT (Izant 1975). SCT has been classified by the relative amounts of presacral and external tumor present in the American Academy of Pediatrics Surgery Section (AAPSS) Classification (Altman et al., 1974). The utility of this classification scheme lies in the relationship between stage and timing of diagnosis, ease of resection, and malignant potential. Type I SCT is evident at birth, is usually easily resected, and has a low malignant potential. Similarly, types II and III SCT are recognized at birth, but resection may be difficult, requiring both anterior and posterior approaches. In type IV SCT, the diagnosis may be delayed until it becomes symptomatic at a later age. Malignant transformation has frequently occurred by the time a type IV SCT is diagnosed. On histologic examination of SCTs, they are categorized as mature, immature, and malignant (Gatcomb 2004). Mature SCTs account for 50 to 60% of all cases and have well differentiated tissues from various sites including sebaceous glands, hair, teeth, bone, or pancreatic Langerhans cell. Immature teratomas have poorly differentiated tissues and primitive neuroectodermal tissue. The earlier the gestational age of the baby, the more likely these will be immature elements in the SCT. SCTs can contain a mixture of well-differentiated mature tissues mixed with immature embryonic tissues. Into this mix, SCTs may also have microscopic rests of malignant elements including a yolk sac tumor, carcinoma, and primitive neuroectodermal (Hereema-McKinney 2005). Incidence SCT is one of the most common tumors in newborns; however, it is still rare, occurring in 1 in 23,000 to 1 in 40,000 livebirths (Schiffer and Greenberg, 1956; Altman et al., 1974; Tapper and Lack, 1983; Forrester and Merz, 2006, Yoon 2005). Females are three to four times more as likely to be affected as males, however, malignant change is more frequently observed in males (Abbott et al., 1966; Conklin and Abell, 1967; Carney et al., 1972; Fraumeni et al., 1973; Altman et al., 1974, Yoon 2005). Sonographic FindingsRetrospective prenatal diagnosis of SCT was first made in the mid-1970s, and the first prospective prenatal diagnosis was reported by Horger and McCarter in 1979. They described a 13-cm complex mass at the caudal end of the fetus, with solid and cystic areas and bizarre internal echoes associated with polyhydramnios. This typical prenatal sonographic appearance has been confirmed by other authors and scores of prenatally diagnosed SCTs have been reported (Seeds et al., 1982; Grisoni et al., 1988; Bond et al., 1990). The most common clinical presentation is uterine size greater than dates, initiating an ultrasound examination (Seeds et al., 1982). To date, the earliest diagnosis of SCT that has been made is 12 3/7 weeks of gestation (Roman et al., 2004). SCTs can grow at an unpredictable rate to tremendous dimensions. Several case reports note fetal tumors as large as 25 by 20 cm (Heys et al., 1967; Weiss et al., 1976). These tumors are generally exophytic (AAPSS type I), but may extend retroperitoneally displacing pelvic (type II) or abdominal structures (type III) (Litwiller, 1969). Most SCTs are solid or mixed solid and cystic, consisting of randomly arranged irregularly shaped cysts (Seeds et al., 1982; Chervenak et al., 1985). Purely cystic SCT has also been described prenatally (Seeds et al., 1982; Hogge et al., 1987). Calcifications can be seen microscopically, although the majority are not visible on prenatal ultrasound examination. Most prenatally diagnosed SCTs are extremely vascular, which is easily demonstrated with the use of color flow Doppler studies. Three-dimensional power Doppler has been suggested to demonstrate the large vascular volume in SCT (Sciaky-Tamir et al., 2006). Polyhydramnios has been noted in most cases of prenatally diagnosed SCT, and—although the mechanisms for this are not known—it is likely secondary to renal hyperfiltration occurring as a result of high-output state (Chervenak et al., 1985). Ultrasound may not be able to define the extent of intrapelvic SCT due to acoustic shadowing by the fetal boney pelvis (Kirkinen 1997). Hepatomegaly, placentomegaly, and nonimmune hydrops have also been seen in association with SCT and appear to be secondary to high-output cardiac failure (Heys et al., 1967; Cousins et al., 1980; Gergely et al., 1980; Kapoor and Saha, 1989; Bond et al., 1990; Flake, 1993; Hedrick et al., 2004). High-output failure may be due to anemia from tumor hemorrhage or arteriovenous shunting within the tumor (Cousins et al., 1980; Flake et al., 1986; Alter et al., 1988; Schmidt et al., 1989; Bond et al., 1990). Some authors have attributed heart failure with subsequent hydrops to severe fetal anemia secondary to tumor hemorrhage (Alter et al., 1988). However, normal fetal hematocrits have also been reported, suggesting that congestive heart failure is more often due to high-output cardiac failure from arteriovenous shunting within the tumor (Schmidt et al., 1989). The demonstration of heart failure or hydrops on ultrasound examination is usually a preterminal event (Flake et al., 1986; Kuhlmann et al., 1987; Bond et al., 1990). Controversy exists regarding the presence of associated anomalies and the need for chromosome analysis. The incidence of coexisting anomalies is 11% to 38%, primarily involving the nervous, cardiac, gastrointestinal, genitourinary, and musculoskeletal systems (Hickey and Layton, 1954; Schiffer and Greenberg, 1956; Carney et al., 1972; Fraumeni et al., 1973; Altman et al., 1974; Izant and Filston, 1975; Gonzalez-Crussi et al., 1978; Ein et al., 1980; Holzgreve et al., 1985; Kuhlmann et al., 1987; Werb et al., 1992). Several authors postulate that at least some of these anomalies are related to tumor development. Others have reported an increased incidence of spinal deformities (Ewing, 1940; Gruenwald, 1941; Alexander and Stevenson, 1946; Bentley and Smith, 1960; Wilson et al., 1963; Carney et al., 1972). Most authors agree with Berry et al.’s (1970) observation that local abnormalities such as rectovaginal fistula and imperforate anus are thought to be directly related to tumor growth during fetal development. SCTs with intrapelvic extension may result in bladder outlet obstruction and dilated urinary tract and even oligohydramnios. Similarly, hydrocolpos, urethrovaginal fistula, rectal atresia, may result from direct compression of the tumor causing ischemic necrosis. The mass-effect of the SCT on pelvic nerves can result in a neurogenic bladder, which may have long-term consequences despite successful SCT resection (Lee 2011). In large SCTs, hip dislocation and sciatic nerve involvement may lead to clubfeet and abnormal leg movements (Yadov 2022). Aneuploidy has not been reported with SCT and we do not recommend amniocentesis for karyotype analysis unless there are multiple anomalies, advanced maternal age, or fetal surgery is contemplated. Prognostic information may be may be obtained sonographically by measured tumor volume to fetal weight ratio (TFR) (Gelb 2019). The TFR is obtained by measuring the greatest dimensions of length, width and height and calculating the volume based on the formula for appropriate ellipse (multiplying length by width by height, and multiplying that sum by 0.5) to devise to fetal weight. A TFR > 0.095 is associated with a poor fetal outcome and a TFR > 0.12 is associated with an increased fetal morbidity and mortality and increased maternal morbidity (Gelb 2019) Another sonographic measurement that is a useful prognostic indicator is the solid-tumor-volume to head-volume ratio (STV/HV ratio). This prognostic ratio was suggested because of the possible influence of the SCT on abdominal circumference used to estimate fetal weight. STV/HV ratio is measured by obtaining the greatest dimension of the SCTs length, width, and depth to calculate a volume using the formula for a prolate ellipse (van Heurn 2021). The volume of the fetal head is measured similarly, and then the tumor volume is divided by the head volume. An STV/HV ratio < 1.0 is associated with fetal survival. Conversely, an STV/HV ratio > 1 is associated with a 61% fetal demise (Cy 2009). The rate of growth of the SCT may also identify fetuses at greatest risk. Coleman et al., found that a growth rate of greater 165 cm3/week had a greater association with high output failure, hydrops, preterm delivery, and death (Coleman 2013). Doppler velocimetry in SCT can be helpful in detecting fetal hemodynamic consequences of SCT. When an SCT is highly vascular, it may “steal” blood flow from the placenta. This occurs due to the presence of low resistance arteriovenous connections within the SCT. This can be seen on Doppler waveforms of the umbilical artery, which normally has positive flow throughout diastole. However in SCTs with vascular “steal” there will be flow reversals in end diastole or throughout diastole as the resistance to flow in the SCT is lower than placental resistance. As high-output failure progresses, the fetal heart decompensates and may develop dysfunction as can be seen with the development of atrioventricular valve incompetence and diastolic dysfunction. Fetal MRIFetal MRI has emerged as an adjunctive imaging modality that can provide important anatomical detail in cases of SCT (Avni et al., 2002; Hedrick et al., 2004; Nassenstein et al., 2006). MRI may be particularly useful in defining the pelvic component of SCT and impact on other pelvic structures (Garel et al., 2005). In cases in which fetal surgery is being considered, fetal MRI provides a broader field of view than ultrasound and may be helpful in operative planning. In cases in which SCT has a pelvic component or there is polyhydramnios, oligohydramnios, hydronephrosis or hydrocolpos, fetal MRI may provide additional information on the anatomical relationships not apparent on ultrasound alone (Danzer et al., 2006). Fetal MRI in cases of cystic SCT may be particularly helpful in excluding myelomeningocele from the differential diagnosis (Yoon and Park, 2005; Danzer et al., 2006). The appearance of solid components of the SCT may be due to either teratoma or hemorrhage into the tumor which can be confirmed on MRI with T1-weighted images. This may be helpful in cases in which there is an evolving high cardiac output state due to anemia. Fetal MRI can be used to measure the entire volume of the SCT (STV/EFW) or specifically, the solid tumor component (STVI). Coleman et al., showed that total tumor volume divided by the estimated fetal weight helps with risk stratification but using the solid tumor volume and STVI is a better predictor of adverse outcome. They found that STVI > 0.9 correlated with a 120-fold increased risk of high-output state or hydrops. In contrast, a total tumor volume to estimated fetal weight ratio > 0.16 correlated with only a 17-fold increased risk of high-output cardiac failure or hydrops. This suggests that solid tumor volume has a much greater impact on predicting adverse outcomes in SCT (Coleman 2013). Fetal EchocardiogramEvery fetus with SCT should have a fetal echocardiogram to exclude structural heart disease and provide baseline assessment of myocardial function, AV valve competence, and combined ventricular output. This baseline is a useful comparator as the SCT evolves and serial echocardiograms will be helpful in early identification of evolving high-output cardiac state or the development of myocardial dysfunction. Differential DiagnosisThe differential diagnosis of SCT includes lumbosacral myelomeningocele, which invariably demonstrates a spinal defect. Myelomeningoceles have a cystic or semicystic rather than a solid appearance and do not contain calcifications. Examination of the fetal brain is helpful in establishing this diagnosis, as most fetuses with lumbosacral myelomeningocele will have associated intracranial findings. Rarer entities that can mimic SCT include neuroblastoma, glioma, hemangioma, neurofibroma, cordoma, leiomyoma, lipoma, melanoma, and any of 50 tumors or malformations reported in the sacrococcygeal region (Lemire and Beckwith, 1982; Sebire et al., 2004; Tanaka et al., 2005). Biochemical markers such as α-fetoprotein (AFP) and acetylcholinesterase are not reliable in distinguishing SCTs from other abnormalities in utero (Holzgreve et al., 1987). It has been suggested, however, that AFP can be used to differentiate benign from malignant tumors, as marked elevations of AFP may reflect the presence of a malignant endodermal sinus component in the tumor (Tsuchilda et al., 1975; Grosfeld et al., 1976; Gonzalez-Crussi et al., 1978; Gonzalez-Crussi, 1982). AFP levels can be extremely high in normal newborns (mean >146,000 ng/ml), limiting the utility of this marker to distinguish benign from malignant lesions (Ohama et al., 1997). Antenatal Natural HistoryThe antenatal natural history of prenatally detected SCT is not as favorable as that of SCT presenting at birth. Well-defined prognostic factors for SCT diagnosed postnatally, as outlined in the AAPSS classification system, do not necessarily apply to fetal cases (Altman et al., 1974; Bond et al., 1990). While the mortality rate for SCT diagnosed in the newborn is at most 5%, the mortality rate for fetal SCT approaches 50% (Flake et al., 1986; Bond et al., 1990; Flake, 1993; Hedrick et al., 2004). Most SCTs are histologically benign. The incidence of malignant elements present in fetal SCT has ranged from 7% to 30% (Hedrick et al., 2004; Heerema-McKenny et al., 2005). Malignancy appears to be more common in males, especially with solid versus complex or cystic tumors (Schey et al., 1977). The presence of histologically immature tissue does not necessarily signify malignancy (Carney et al., 1972; Gonzalez-Crussi, 1982). Calcifications occur more often in benign tumors but may also be seen in malignant tumors and are unreliable indicators of malignant potential (Hickey and Layton, 1954; Waldhausen et al., 1963; Grosfeld et al., 1976; Schey et al., 1977; Horger and McCarter, 1979). Although there have been reported case of malignant yolk sac differentiation in a fetal SCT, there has not been a case of metastatic teratoma in a neonate with a prenatally diagnosed SCT (Holzgreve et al., 1985; Flake, 1993). The prenatal history of SCT is quite different from the postnatal natural history. Flake et al. (1986) reviewed 27 cases of prenatally diagnosed SCT. Five cases were electively terminated and 15 of the remaining 22 died, either in utero or shortly after delivery. The majority of these patients presented between 22 and 34 weeks of gestation with a uterus large for gestational age secondary to severe polyhydramnios. The presence of hydrops and/or polyhydramnios was associated with intrauterine fetal death in seven of seven cases. The International Fetal Medicine and Surgery Society reported a mortality rate of 52% among cases of prenatally diagnosed SCT (Bond et al., 1990). When SCT was seen in association with placentomegaly or hydrops, all affected fetuses died in utero. The indication for ultrasound examination was also found to be a predictive factor. If SCT was an incidental finding, the prognosis was favorable at any gestational age. However, if the ultrasound examination was performed for maternal indications, 22 of 32 fetuses died. In addition, diagnosis prior to 30 weeks was associated with a poor outcome. Sheth et al. (1988) also reported significant perinatal mortality associated with SCT, with only 6 survivors among 15 cases diagnosed prenatally. Three of four cases associated with hydrops were rapidly fatal. The sole survivor was salvaged by emergency cesarean section at 35 weeks. This series was unusual because three cases had severe obstructive uropathy and secondary renal dysplasia. A more favorable outcome was reported by Gross et al. (1987) in which 8 of 10 fetuses with prenatally diagnosed SCT survived. However, no fetus had hydrops or placentomegaly, and the two nonsurvivors were electively terminated. Hydrops in SCT is usually, but not always, fatal. Nakoyama et al. (1991) reported survival in two fetuses with SCT presenting with hydrops at 27 and 30 weeks of gestation. In addition, Robertson et al. (1995) were able to salvage a hydropic fetus at 26 weeks of gestation by staged resection of the SCT in the neonatal period. In this case, acute rapid growth of the SCT led to polyhydramnios and preterm delivery. After delivery, the newborn was noted to be in a high-output state from shunting through the tumor. In a staged resection, the tumor was initially devascularized by ligation of both internal iliac arteries. Thirty-six hours later, the external portion of the mass was resected. The infant subsequently underwent resection of the intrapelvic portion of the tumor at 3 months of age, and did well. Hedrick et al. (2004) reviewed their experiences with 30 cases of prenatally diagnosed SCT and reported 4 terminations, 5 fetal deaths, 7 neonatal deaths, and only 14 survivors (47%). Among the 26 patients continuing the pregnancy, 81% experienced obstetric complications including polyhydramnios (n = 7), oligohydramnios (n = 4), preterm labor (n = 13), preeclampsia (n = 4), gestational diabetes (n = 1), HELLP syndrome (n = 1), and hyperemesis (n = 1). Sonographic features of SCT such as size, AAPSS classification, solid or cystic composition, or presence or absence of calcifications have not been predictive of either fetal survival or future malignant potential (Altman et al., 1974; Flake, 1993). One exception to this may be the predominantly cystic form of SCT, which has a relatively favorable prognosis because of benign histology and limited vascular and metabolic demand (Horger and McCarter, 1979; Mintz et al., 1983). The growth of the SCT in relation to the size of the fetus is also unpredictable and may increase, decrease, or stabilize as gestation proceeds. However, a rapid phase of tumor growth usually precedes the development of placentomegaly and hydrops. Highly vascular lesions are more likely to undergo rapid tumor growth and to be associated with the development of placentomegaly and hydrops. The prenatal mortality, unlike postnatal mortality, is not due to malignant degeneration, but to complications of tumor mass or tumor physiology (Flake et al., 1993). The tumor mass may result in malpresentation or dystocia, which in turn may result in tumor rupture and hemorrhage during delivery. Dystocia has been reported in 6% to 13% of cases in postnatal series (Giugiaro et al., 1977; Musci et al., 1983; Gross et al., 1987). SCTs may also spontaneously rupture in utero leading to significant fetal anemia or death (Sy et al., 2006). The most important benefit of prenatal diagnosis is prevention of dystocia by elective or emergency cesarean section. Tumor mass effect may also result in uterine irritability and preterm delivery because of uterine distention (Flake et al., 1986; Bond et al., 1990). Massive polyhydramnios is frequently seen in large fetal SCT, which also predisposes to uterine irritability and preterm delivery. SCT may occur in twins further complicating the prenatal management. In Hedrick et al.’s series, 10% of the cases occurred in twin gestations (Hedrick et al., 2004). The presence of SCT in a twin gestation increases the risk of preterm delivery. Because SCT is associated with an increased risk of fetal death, intrauterine demise of a monochorionic twin with SCT places the surviving unaffected co-twin at risk of adverse neurologic outcome (Ayzen et al., 2006). The physiologic consequence of fetal SCT depends on the metabolic demands of the tumor, blood flow to the tumor, and the presence and degree of anemia. The features of the SCT—whether cystic or solid, size, and rate of growth—all affect the metabolic demands of fetal SCT. While classically thought to derive its blood supply from the middle sacral artery (Smith et al., 1961), these large tumors often parasitize blood supply from the internal and external iliac systems. This may result in vascular “steal” from the umbilical artery blood flow to the placenta. As an SCT outgrows its blood supply, tumor necrosis may occur leading to tumor rupture and hemorrhage. The high-output cardiac failure in fetal SCT can be diagnosed by fetal echocardiography (Flake et al., 1986; Langer et al., 1989; Schmidt et al., 1989). When hydrops develops in fetuses with SCT, all have dilated ventricles and dilated inferior venae cavae due to increased venous return from the lower body (Flake, 1993). Serial sonographic examinations in fetal SCT often show progressive increases in combined ventricular output and descending aortic flow velocity. In general, placental blood flow is decreased by the vascular steal by the SCT (Schmidt et al., 1989; Flake, 1993) and may lead to the finding of end-diastolic flow reversals in the umbilical artery. Benachi et al. (2006) have suggested a prenatal prognostic classification system based on tumor diameter, vascularity, and rapidity of growth. In a group of 44 fetal SCTs divided into group A (tumor < 10 cm, absent or mild vascularity and slow growth), group B (tumor ≥ 10 cm, pronounced vascularity or high output cardiac failure and rapid growth), and group C (tumor ≥ 10 cm, predominantly cystic lesion with absent or mild vascularity and slow growth), Groups A and C did well with gestational age at delivery of 38 and 37 weeks, respectively, while group B delivered prematurely at 31 weeks of gestation. There was no mortality in either group A or C but was 52% for group B. The newborns in group B also have a much longer length of stay postnatally (Benachi et al. 2006). Postnatal measurements of umbilical arterial blood gases before and after removal of a large SCT demonstrate that the tumor acts as a large arteriovenous shunt. Management of PregnancyAlthough the primary cause of death in neonatally diagnosed SCT is malignant invasion, in prenatally diagnosed SCT, the complications of prematurity or exsanguinating tumor hemorrhage at delivery predominate (Flake et al., 1986; Bond et al., 1990; Adzick and Harrison, 1994). Weekly sonographic examinations should be performed during pregnancy to assess amniotic fluid index, tumor growth, fetal well-being, and early evidence of hydrops (Chervenak et al., 1985; Langer et al., 1989). Serial Doppler echocardiographic evaluations should be performed in all patients to detect early signs of high-output state, as evaluated by an increased diameter of the inferior vena cava (>6mm), increased descending aortic flow velocity (>120 cm/s) (Alter et al., 1988; Flake, 1993; Bahlmann et al., 2001), or increased combined ventricular output (>600 mL/kg/min for CVO) (Bahlmann et al., 2001, Hedrick 2004). Evidence of the earliest signs of heart failure, placentomegaly, and/or hydrops should be sought, as these may progress rapidly and are harbingers of preterminal events (Langer et al., 1989). Bond et al. (1990) reported a uniformly fatal outcome when SCT was associated with placentomegaly and/or hydrops. Flake et al. (1986) reported seven of seven fetal deaths in pregnancies complicated by placentomegaly and hydrops. Warning signs and symptoms of preterm labor should be stressed at prenatal visits, and limitation of activity and cervical checks may be indicated (Garmel et al., 1994). The recommended mode of delivery is determined by the size of the tumor. Vaginal delivery may be possible with some small tumors (Grisoni et al., 1988; Flake, 1993). Complications of vaginal delivery, however, have included fetal death after rupture, avulsion, or asphyxia (Schiffer and Green-berg, 1956; Heys et al., 1967; Grosfeld et al., 1976; Giugiaro et al., 1977; Chervenak et al., 1985; Holzgreve et al., 1987; Werb et al., 1992). Cesarean delivery is recommended to avoid trauma-induced hemorrhage or dystocia, especially in large (>5-10 cm) tumors (Chervenak et al., 1985; Gross et al., 1987; Hogge et al., 1987; El-Qarmalaui et al., 1990; Flake, 1993). The size of the tumor may also influence the type of uterine incision. A large tumor may warrant a classical uterine incision, especially in a preterm infant (Chervenak et al., 1985). Dystocia has been reported when the diagnosis of SCT was unsuspected in as many as 6% to 13% of cases (Hickey and Layton, 1954; Schiffer and Greenberg, 1956; Seidenberg and Hurwitt, 1958; Lowenstein et al., 1963; Hickey and Martin, 1964; Abbott et al., 1966; Lu and Lee, 1966; Heys et al., 1967; Desai, 1968; Kowalski and Sokolowska-Pituchowa, 1968; Werner and Swiecicka, 1968; Litwiller, 1969; Weiss et al., 1976; Seeds et al., 1982; Tanaree, 1982; Edwards, 1983; Mintz et al., 1983; Musci et al., 1983; Varga et al., 1987; El-Shafie et al., 1988; Johnson et al., 1988). Transabdominal and transvaginal aspirations of large cysts have been attempted with variable results to facilitate delivery in the face of significant dystocia (Abbott et al., 1966; Desai, 1968; Litwiller, 1969; Weiss et al., 1976; Tanaree, 1982; Edwards, 1983; Mintz et al., 1983; Musci et al., 1983; El-Shafie et al., 1988; Johnson et al., 1988). Cyst decompression has also been used to treat maternal discomfort, and in one case cyst amniotic shunting was used to treat bladder outlet obstruction due to tumor compression (Garcia et al., 1998; Kay et al., 1999; Jouannic et al., 2001). It is hoped that prenatal detection of SCT will prevent such unforeseen emergencies (Musci et al., 1983). Fetal SCT is sometimes associated with maternal complications. The mother should be observed for signs and symptoms of preeclampsia, such as the “mirror syndrome” described by Nicolay et al. in association with SCT and hydrops (Nicolay and Gainey, 1964; Cousins et al., 1980; Flake et al., 1986; Coleman et al., 1987; Langer et al., 1989; Bond et al., 1990). The mother needs to be observed for signs of maternal mirror syndrome characterized by massive third spacing and pulmonary edema. In addition, these mothers are at risk for mild to severe preeclampsia including HELLP (hemolysis elevated liver enzymes, low platelets) syndrome. Delivery should be performed in a tertiary care center, with neonatologists and pediatric surgeons available. Fetal InterventionThe uniformly dismal outcome in fetuses with SCT complicated by placentomegaly and hydrops has been the impetus for resection of this tumor in utero. Harrison was the first to attempt antenatal resection of an SCT (Langer et al., 1989). In this first case, a fetus was noted to be markedly hydropic with a significantly elevated combined ventricular output (972 mL/kg/min) at 24 weeks (Langer et al., 1989; Flake, 1993). In addition, the mother had mild hypertension, edema, and proteinuria. Preterm labor developed that was controlled with tocolytic agents. At surgery, the exophytic portion of the tumor was dissected free of the anus and rectum and amputated at its base with a stapling device. Despite the resection, the fetus remained hydropic, with an elevated combined ventricular output of 869 mL per kilogram of body weight per minute. Percutaneous umbilical cord blood sampling showed the fetal hematocrit to be only 16%. This was increased to 27% by blood transfusion. The fetus subsequently improved significantly, with sonographic resolution of hydrops, and a decrease in descending aortic flow to 524 mL/kg of body weight per minute. However, the maternal mirror syndrome progressed to pulmonary edema and on postoperative day 12, a 26-week-gestation fetus was delivered by cesarean section and died of pulmonary immaturity at 6 hours of age. The mother’s illness resolved within 2 days. Autopsy showed no evidence of hydrops and no residual tumor. A second case was attempted at 26 weeks of gestation, when dramatic enlargement of the tumor resulted in early hydrops, elevated combined ventricular output, and severe polyhydramnios (Flake, 1993). The surgery went uneventfully, and the base of the tumor was stapled to excise the exophytic portion and reverse the hyperdynamic state. The fetus did well until postoperative day 8, when irreversible preterm labor developed and the fetus was delivered by emergency cesarean section. Because the histology of the resected specimen was interpreted as an immature teratoma grade III/III, with predominance of neuroepithelial elements and foci of yolk sac differentiation, resection of residual tumor was attempted on the 13th day of postnatal life. During dissection of the presacral space, the baby experienced complete cardiovascular collapse due to a paradoxical air embolism. The histology of the tumor revealed grade III/III immature teratoma, but the residual tumor was more mature than the previous tumor specimen and contained no foci of yolk sac differentiation. The first successful resection of fetal SCT with long-term survival was reported by Adzick and Crombleholme (1997). At 25 weeks of gestation, a type II SCT had rapid enlargement and development of polyhydramnios and placentomegaly, with associated maternal tachycardia and proteinuria suggesting impending maternal mirror syndrome. At surgery, the exophytic portion of the tumor was dissected free of the anus and rectum and the base of the tumor excised with a thick tissue stapling device. The mother and fetus did well postoperatively, with resolution of hydrops and placentomegaly within 10 days. Pathology of the tumor showed grade III/III immature teratoma without evidence of yolk sac differentiation. At 29 weeks of gestation preterm labor prompted cesarean delivery. Postnatally, the female infant underwent resection of the coccyx and surrounding tissue at 2 months of age, but no residual tumor was found. She did well until 1 year of age when AFP levels became elevated to 22,000 ng/mL and she presented with pleural effusions, lung nodules, and a recurrent buttock mass from a metastatic yolk sac tumor. She has had an excellent response to chemotherapy. Hedrick et al. subsequently reported our experience with four open fetal surgeries for SCT with all four surviving the procedure to delivery at an average gestational age of 29 weeks (range 27.6–31.7 weeks). There was one neonatal death due to in utero closure of the ductus arteriosus thought to be secondary to indomethacin exposure as a tocolytic agent following fetal surgery. Other complications experienced in these fetal surgery patients included tumor embolism resulting in renal infarction and multiple jejunal atresias (n = 1), chronic lung disease (n = 1), and development of metastatic endodermal yolk sac tumor (n = 1) (Hedrick et al., 2004). While clinical experience remains limited, there have been other cases of SCT successfully resected in utero at the University of California, San Francisco and at Cincinnati Children’s Hospital. For the fetus with a large SCT associated with early signs of hydrops or placentomegaly, resection in utero remains a viable option. Primary resection of the external portion of the tumor was performed with interval resection of the pelvic extension of SCT. This approach may be useful in managing the common association of prematurity, large tumor, and hyperdynamic state. Because the primary cause of fetal mortality and morbidity is the vascular shunting through the tumor, there have been attempts to embolize or devascularize the tumor using radiofrequency ablation (Paek et al., 2001; Lam et al., 2002). In a report of four patients treated with radiofrequency ablation, two fetuses died secondary to hemorrhage after a significant portion of the tumor mass was ablated. The remaining two fetuses delivered at 28 and 31 weeks gestation with evidence of extensive necrosis of pelvic and perineal structures, necessitating extensive reconstructive surgery (Ibrahim et al., 2003). The uncontrolled nature of the energy delivered by the radiofrequency ablation device prevents its safe application in SCT, and this treatment modality has been abandoned by most centers. Interstitial laser photocoagulation has also been applied in the treatment of 10 cases of hydropic sacrococcygeal teratoma (SCT). The rationale for interstitial laser treatment of SCT is that the hyper-vascular SCT results in arterio-venous shunting through the mass with cardiac overload from high output failure resulting in hydrops and placental steal. Photocoagulation of vessels feeding the SCT will temporarily reduce blood flow to the tumor. However, re-treatment will be necessary as other collateral vessels are parasitized by the SCT and the high output state will recur. Two cases developed PPROM and all 8 delivered prior to 32 weeks’ gestation. Fetal demise (n=4) and neonatal demise (n=2) occurred in 6 of the 10 treated SCTs with an overall survival of only 4 of 10. Temporizing treatment of the SCT by repeated ultrasound guided interstitial laser photocoaguation may reverse the hydrops caused by high-output cardiac failure if the arteriovenous shunting through the SCT can be reduced. Even if additional shunting occurs through subsequent formation of new arteriovenous shunts, this approach may buy significant amount of time and allow the pregnancy to get further along. Most SCTs get into trouble with hydrops between 23 and 27 weeks, and any additional time in utero may reduce complications related to prematurity. The rationale for this approach is that it can selectively target arterial perfusion to the exophytic portion of the SCT with minimal injury to adjacent tissues. Crombleholme developed the following criteria for ultrasound-guided interstitial laser treatment of SCTs including: 1.) treatment prior to the onset of hydrops; 2.) elevated combined ventricular output of > 600 mL/kg/min; 3.) treat only arteries in the exophytic portion of the SCT to prevent injury to normal pelvic structures; 4) treat only vessels surrounded by tissue so that if the vessel ruptures, it will be tamponaded by tissue and will not continue to bleed (we avoid treating surface vessels which would continue to bleed if they ruptured); 5) treat only arteries to avoid venous hypertension which would result from treating the draining veins and may predispose to hemorrhage into the SCT or embolization. Among the challenges of treating large type II and type III SCTs is the difficulty in keeping the mother pregnant. Despite technically successful open fetal surgeries to resect the SCT, preterm labor or the development of maternal mirror syndrome often necessitated very premature delivery. Recognizing the difficulty in trying to keep the mother pregnant after performing open fetal surgery for SCT, we undertook observation until the mother developed active labor and had an emergent cesarean delivery with larger hysterotomy to prevent trauma to the SCT. In a series of 4 patients, the babies were in full cardiac arrest by the time they were given to the neonatologist due to hemorrhage into the tumor. We attempted tourniquet to prevent ongoing blood loss and assist resuscitation, even emergent resection in the delivery room, with no survivors. Subsequent to this experience, we have performed EXIT-to-Resection for type II and III SCT removing the external portion of the SCT, which interrupts the vascular communications and stabilizes the high output state. We perform an interval resection of residual SCT when the premature baby reaches equivalent of 40 post-conceptual weeks. If malignant rests are found on pathology then the timing of the resection of residual SCT can be moved up. Of the 9 babies with SCT, 8 managed in this way have survived and are without recurrence of SCT or endodermal sinus tumor with 1 to 7 years of follow up. The only non-survivor, died as a result of a hypoplastic airway too small to be intubated even with a 2.O endotracheal tube, not as a result of the SCT or its treatment. Treatment of the NewbornA neonatologist should attend the delivery and be prepared to provide respiratory hemodynamic support. Careful handling of the infant is important to prevent exsanguinating hemorrhage into the tumor. Excellent venous access is paramount should hemorrhage in the tumor occur, and umbilical artery and umbilical venous catheters should be placed. The infant should be started on pressor agents such as dopamine or epinephrine to support the heart depending on its hemodynamic state. Transfusion may be necessary immediately postnatally because hemorrhage into the tumor may have occurred during the delivery. Severely premature infants should be intubated and treated for respiratory distress with surfactant-replacement therapy. Echocardiography should be obtained to assess the cardiac status of the newborn. Abdominal ultrasound examination can be performed at the bedside to assess the intrapelvic or intra-abdominal extent of tumor. If there is no evidence of high-output state, then there is no urgency to resect the tumor, and attention should focus on the treatment of respiratory distress and correction of anemia. If a hyperdynamic state exists with an elevated cardiac output, attention should focus on supporting the newborn heart with inotropic agents and urgent resection of the SCT when stable. Surgical TreatmentThe goal of this resection is reversal of the high-output state, and this can usually be accomplished by resection of the exophytic portion of the tumor. Initial proximal aortic control by Rommel tourniquet using a vessel loop can be lifesaving when resecting a large vascular SCT in a severely premature infant (Robertson et al., 1995). Preoperative angiography and embolization and radiofrequency ablation have been used successfully as adjuncts to surgical resection of large vascular SCTs (Cowles et al., 2006). As with fetal resection of SCT, SCT resection in a premature infant should focus on eliminating the cause of the high-output state, not necessarily complete tumor resection. This can be accomplished by utilization of a thick tissue stapling device at the base of the SCT. If residual pelvic tumor remains, the urgency of resection can be guided by the pathology. The presence of yolk sac differentiation may necessitate earlier resection. In the absence of yolk sac differentiation, however, several months of growth of the infant can facilitate subsequent resection of the coccyx and the intrapelvic or intra-abdominal portion of the tumor. An anterior-posterior approach may be required for resection of the pelvic and abdominal tumor. The operating table should be kept in a slight reverse Trendelenburg position to prevent air embolism (Seeds et al., 1982). Staged resection may also be considered. In one report, a fetus in a high-output state due to an SCT 1.5 times the size of the baby underwent initial devascularization via ligation of the middle sacral and internal iliac arteries that eliminated the hyperdynamic high-output state and returned cardiac output to normal (Robertson et al., 1995). Thirty-six hours later, primary resection of the residual tumor was performed. The infant subsequently underwent resection of the intrapelvic portion of the tumor at 2 months of age, and 4 years later was free of disease. Massive hemorrhage is an important cause of neonatal death in large vascular SCTs undergoing resection. Coagulapathy resulting from massive hemorrhage may be an important contributing factor. Recombinant factor VIIa has been used successfully in this setting (Girisch et al., 2004). Long-Term OutcomeThe long-term outcome in newborns with SCT is generally excellent. The most important prognostic factor for SCT appears to be the age at diagnosis (Conklin and Abell, 1967). When the diagnosis is made prior to 2 months of postnatal age, or excision is performed prior to 4 months of age, the malignant potential is only 5% to 10% (Gross et al., 1951; Hickey and Layton, 1954; Waldhausen et al., 1963; Donnel-lan and Swenson, 1988). This increases to 50% to 90% if the diagnosis is delayed until after 2 to 4 months of age (Hickey and Layton, 1954; Altman et al., 1974). The mortality in a newborn with SCT is, however, not primarily due to malignant potential, but rather from difficulty in resection, and possibility of tumor hemorrhage (Altman et al., 1974; Schey et al., 1977; Alter et al., 1988; Grisoni et al., 1988). Gestational age at diagnosis may also affect prognosis, as fetuses diagnosed with SCT after 30 weeks of gestation tend to fare better than those diagnosed earlier (Schey et al., 1977; Flake et al., 1986; Kuhlmann et al., 1987). Cystic tumors may carry a better prognosis, most likely because of the lower incidence of tumor hemorrhage or vascular steal (Hogge et al., 1987). Prompt excision of both the tumor and the coccyx is thought to be essential to prevent recurrence (Gross et al., 1987). Delay may result in infection, hemorrhage, pressure necrosis, and malignant degeneration (Holzgreve et al., 1985). Although SCTs are usually benign, they are prone to recurrence and have malignant potential. Long-term surveillance for tumor recurrence is essential. In SCTs, AFP levels are a useful marker for possible recurrence. A consistent downward trend in values should be observed until normal levels are reached by 1 year of age. We currently recommend that all newborns with SCT have serum AFP levels measured and physical examinations performed, including digital rectal examinations, every 3 months. Such surveillance is recommended for at least 3 years (Barreto et al., 2006). If the SCT was nonfunctional, postnatal pelvic sonographic examinations should be obtained at similar intervals. In addition, MRI should be obtained on at least a yearly basis. Any increase over previous AFP values should prompt investigation for possible recurrence. Factors that were thought to increase risk of recurrence of SCT or malignant yolk sac tumor were immature and malignant histology or incomplete resection. The chances of this recurrence was estimated at 11% by Derikx et al. (2006). Recurrence of the tumor does not necessarily indicate recurrence of malignancy. It should be treated as a premalignant lesion and excised. Even with malignant transformation of SCT, results with current chemotherapeutic regimens have achieved excellent survival rates. Misra et al. (1997) reported survival rates of 88% with local disease and 75% even in the face of distant metastases. If the pathologic examination of the SCT reveals microscopic rests of endodermal sinus tumor, it remains controversial as to whether chemotherapy is indicated (Heerema-McKenney et al., 2005). Older studies suggested any amount of yolk sac tumor presaged a poor prognosis and aggressive treatment was indicated (Valdiserri and Yunis, 1981; Rescorla et al., 1998). More recent studies suggest the presence of yolk sac tumor, foci of fetal lines, and immature endodermal glands in the SCT are associated with an increased risk of recurrent yolk sac tumor (Hawkins et al., 1993; Heifetz et al., 1998). Those recurrences however are amenable to modern combination chemotherapy with excellent survival (Rescorla et al., 1998; Marina et al., 1999; Huddart et al., 2003; Heerema-McKenney et al., 2005; De Backer et al., 2006). There is limited long-term outcome data in SCT patients. Fortunately, with smaller benign SCT, there is usually no serious bowel or bladder dysfunction after surgery and most neonates do well following resection (Litwiller, 1969; Tapper and Lack, 1983; Gross et al., 1987). Neurogenic bladder, however, is not an uncommon sequela in SCTs with a large pelvic component. Ozkan et al. reported a series of 14 cases of neurogenic bladder with high-grade reflux with abnormal bladder and urethral function following resection of SCTs (Ozkan et al., 2006). Similarly, postoperative urologic sequelae in SCT have ranged from 20% to 30% (Kirk and Lister, 1976; Lahdenne et al., 1992; Carr et al., 1997). In type II and III SCTs there is a very high incidence of urinary tract abnormalities including neurogenic bladder and severe vesico-ureteral reflux (Cost et al, Lee et al 2011 ). Urologic functional recovery has been documented with increasing age (Engelskirchen et al., 1987; Carr et al., 1997). Bittmann and Bittman found 33% had impaired bowel and bladder function. The frequency of anorectal dysfunction has ranged up to 40% (Engelskirchen et al., 1987; Malone et al., 1990; Wooley, 1993; Boemers et al., 1994, Partridge 2014). The most common long-term complication after SCT resection was cosmetic dissatisfaction with operative closure (Bittmann and Bittmann, 2006). Some children may experience subtle gait abnormalities as a result of the mass effect on the sciatic nerve by the SCT or injury during its resection (Zaccara et al., 2004). Genetics and Recurrent RiskSome cases of SCT appear to be familial, with a suggestion of an autosomal dominant inheritance (Hunt et al., 1977; Gonzalez-Crussi, 1982). Familial SCTs are more often type IV SCTs and can be easily missed (Gopal et al., 2007). While only 10% of nonfamilial SCTs are presacral, 100% of familial SCTs are presacral. Familial cases have a male to female rate of 1:1 compared to 1:4 ratio in nonfamilial cases. Familial cases can be associated with anorectal malformations, most commonly anal stenosis, and can present as part of Currarino’s triad (presacral tumor, anorectal malformation, and sacral anomaly) (Currarino et al., 1981). The familial cases are more likely to be associated with a “scimitar sacrum” and are usually benign (Gopal et al., 2007). There have been rare cases of chromosomal abnormalities reported in patients with SCT including distal 10q trisomy syndrome (Batukan et al., 2007), mosaic trisomy of the long arm of chromosome 1 (Wax et al., 2000), and de novo translocation between chromosome 2 and 7 (Le Caignec et al., 2003). ReferencesAbbott PD, Bowman A, Kantor HI. Dystocia caused by sacrococcygeal teratoma. Obstet Gynecol. 1966;27:571-579. Adzick NS, Crombleholme TM, Morgan MA, Quinn TM. A rapidly growing fetal teratoma. Lancet. 1997;349:538. Adzick NS, Harrison MR. The unborn surgical patient. Curr Probl Surg. 1994;35:1. Alexander CM, Stevenson LD. Sacral spina bifida, intrapelvic meningocele, and sacrococcygeal teratoma. Am J Clin Pathol. 1946;16:466-471. Alter DN, Reed KL, Marx GR, Anderson CF, Shenker L. Prenatal diagnosis of congestive heart failure in a fetus with a sacrococcygeal teratoma. Obstet Gynecol. 1988;71:978-981. Altman RP, Randolph JG, Lilly JR. Sacrococcygeal teratoma. American Academy of Pediatrics Surgical Section Survey—1973. J Pediatr Surg. 1974;9:389-398. Ashley DJB. Origin of teratomas. Cancer. 1973;32:390-394. Avni FE, Guibaud L, Robert Y, et al. MR imaging of fetal sacrococcygeal teratoma: diagnosis and assessment. AJR Am J Roentgenol. 2002;178:179-183. Ayzen M, Ball R, Nobuhara KK, et al. Monochorionic twin gestation complicated by a sacrococcygeal teratoma with hydrops—optimal timing of delivery allows survival of the unaffected twin. J Pediatr Surg. 2006;41:E11-E13. Bahlmann F, Wellek S, Reinhardt I, et al. Reference values of fetal aortic flow velocity waveforms and associated intra-observer reliability in normal pregnancies. Ultrasound Obstet Gynecol. 2001;17:42-49. Bale PM. Sacrococcygeal developmental abnormalities and tumors in children. Perspect Pediatr Pathol. 1984;1:9-56. Barreto MW, Silva LV, Barini R, et al. Alpha-fetoprotein following neonatal resection of sacrococcygeal teratoma. Pediatr Hematol Oncol. 2006;23:287-291. Batukan C, Ozgun MT, Basbug M, et al. Sacrococcygeal teratoma in a fetus with prenatally diagnosed partial trisomy 10q (10q24.3→qter) and partial monosomy 17p (p13.3→pter). Prenat Diagn. 2007;27:365-368. Benachi A, Durin L, Maurer SV, et al. Prenatally diagnosed sacrococcygeal teratoma: a prognostic classification. J Pediatr Surg. 2006;41:1517-1521. Bentley JFR, Smith JR. Developmental posterior enteric remnants and spinal malformations. Arch Dis Child. 1960;35:76-86. Berry CL, Keeling J, Hilton C. Coincidence of congenital malformation and embryonic tumours of childhood. Arch Dis Child. 1970;45:229-231. Bittman S, Bittmann V. Surgical experience and cosmetic outcomes in children with sacrococcygeal teratoma. Curr Surg. 2006;63:51-54. Boemers TM, van Gool JD, de Jong TP, et al. Lower urinary tract dysfunction in children with benign sacrococcygeal teratoma. J Urol. 1994;151:174-176. Bond SJ, Harrison MR, Schmidt KG, et al. Death due to high-output cardiac failure in fetal sacrococcygeal teratoma. J Pediatr Surg. 1990;25:1287-1291. Carney JA, Thompson DP, Johnson CL, Lynn HB. Teratomas in children: clinical and pathologic aspects. J Pediatr Surg. 1972;7:271-282. Carr MM, Thorner P, Phillips JH. Congenital teratomas of the head and neck. J Otolaryngol. 1997;26:246-252. Chervenak FA, Isaacson G, Touloukian R, et al. Diagnosis and management of fetal teratomas. Obstet Gynecol. 1985;66:666-671. Coleman BG, Grumbach K, Anger PH, et al. Twin gestations: monitoring of complications and anomalies with US. Radiology. 1987;165:449-453. Coleman A, Shaaban A, Keswani S, Lim FY. Sacrococcygeal teratoma growth rate predicts adverse outcomes. J Pediatr Surg. 49(6), 985-989 (2014). Conklin J, Abell MR. Germ cell neoplasms of sacrococcygeal region. Cancer. 1967;12:2105-2117. Cost NG, Geller JI, Le LD, Crombleholme TM, Keswani SG, Lim FY, Alam S: Urologic co-morbidities associated with sacroccocygeal teratoma and a rational plan for urologic surveillance. Pediatr Blood Cancer 2013; 60: 1626-1629 Cousins L, Benirschke K, Porreco R, Resnik R. Placentomegaly due to fetal congestive failure in a pregnancy with a sacrococcygeal teratoma. J Reprod Med. 1980;25:142-144. Cowles RA, Stolar CJ, Kandel JJ, et al. Preoperative angiography with embolization and radiofrequency ablation as novel adjuncts to safe surgical resection of a large, vascular sacrococcygeal teratoma. Pediatr Surg Int. 2006;22:554-556. Currarino G, Coln D, Votteler T. Triad of anorectal, sacral, and presacral anomalies. AJR Am J Roentgenol. 1981;137:395-398. Danzer E, Hubbard AM, Hedrick HL, et al. Diagnosis and characterization of fetal sacrococcygeal teratoma with prenatal MRI. AJR Am J Roentgenol. 2006:187;W350-W356. De Backer A, Madern GC, Friederike GAJ, et al. Study of the factors associated with recurrence in children with sacrococcygeal teratoma. J Pediatr Surg. 2006;41:173-181. Derikx JPM, De Backer A, van de Schoot L, et al. Factors associated with recurrence and metastasis in sacrococcygeal teratoma. Br J Surg. 2006;93:1543-1548. Desai V. Dystocia due to fetal sacrococcygeal teratoma. J Obstet Gynaecol Br Commonw. 1968;75:1074-1075. Donnellan WA, Swenson O. Benign and malignant sacrococcygeal teratomas. Pediatr Surg. 1988;64:834-846. Edwards WR. A fetal sacrococcygeal tumor obstructing labor after attempted home confinement. Obstet Gynecol. 1983;61:19S-21S. Ein SH, Adeyemei SD, Mancer K. Benign sacrococcygeal teratomas in infants and children. Ann Surg. 1980;191:382-384. El-Qarmalaui MA, Saddik M, El Abdel Hadi F, Muwaffi R, Nageeb K. Diagnosis and management of fetal sacrococcygeal teratoma. Int J Gynecol Obstet. 1990;31:275-281. El-Shafie M, Naylor D, Schaff E, Conrad M, Miller D. Unexpected dystocia secondary to a fetal sacrococcygeal teratoma: a successful out-come. Int J Gynecol Obstet. 1988;27:431-438. Engelskirchen R, Holschneider AM, Rhein R, et al. Sacrococcygeal teratomas in children: an analysis of long-term results in 87 cases. Z Kinderchir. 1987;18:294-361. Ewing J. Neoplastic Diseases: A Textbook on Tumors. 4th ed. Philadelphia, PA: WB Saunders; 1940. Flake AW. Fetal sacrococcygeal teratoma. Semin Pediatr Surg. 1993;2:113-120. Flake AW, Harrison MR, Adzick NS, Laberge J, Warsof SL. Fetal sacrococcygeal teratoma. J Pediatr Surg. 1986;21:563-566. Forrester MB, Merz RD. Descriptive epidemiology of teratoma in infants, Hawaii, 1986–2001. Paediatr Perinat Epidemiol. 2006;20: 54-58. Fraumeni JR, Li FP, Dalager N. Teratomas in children: epidemiologic features. J Natl Cancer Inst. 1973;1425-1430. Garcia AM, Morgan WM III, Bruner JP. In utero decompression of a cystic grade IV sacrococcygeal teratoma. Fetal Diagn Ther. 1998;13:305-308. Garel C, Mizouni L, Menez F, et al. Prenatal diagnosis of a cystic type IV sacrococcygeal teratoma mimicking a cloacal anomaly: contribution of MR. Prenat Diagn. 2005;25:216-219. Garmel SH, Crombleholme TM, Semple J, et al. Prenatal diagnosis and management of fetal tumors. Semin Perinatol. 1994;18:350-365. Gatcombe HG, Assikis V, Kooby D, Johnstone, PAS. Primary retroperitoneal teratomas: a review of the literature. J Surg Oncol 86, 107-113 (2004). Gebb JS, et al. High Tumor Volume to Fetal Weight Ratio Is Associated with Worse Fetal Outcomes and Increased Maternal Risk in Fetuses with Sacrococcygeal Teratoma. Fetal Diagn Ther.45(2), 94-101 (2019). Gergely RZ, Eden R, Schifrin BS, Wade ME. Antenatal diagnosis of congenital sacral teratoma. J Reprod Med. 1980;24:229-231. Girisch M, Rauch R, Carbon R, et al. Refractory bleeding following major surgery of a giant sacrococcygeal teratoma in a premature infant: successful use of recombinant factor VIIa. Eur J Pediatr. 2004;163:118-119. Giugiaro A, Boario U, DiFrancesco G, Freni G. Considerazioni su tre casi di rottura intraparto di teratoma sacrococcigeo. Minerva Pediatr. 1977;29:1517-1524. (English summary.) Gonzalez-Crussi F. Extragonadal Teratomas. Atlas of Tumor Pathology. 2nd Series, Fascicle 18. Bethesda, MD: Armed Forces Institute of Pathology; 1982:50-76. Gonzalez-Crussi F, Winkler RF, Mirkin DL. Sacrococcygeal teratomas in infants and children. Arch Pathol Lab Med. 1978;102:420-425. Gopal M, Turnpenny PD, Spicer R. Hereditary sacrococcygeal teratoma—not the same as its sporadic counterpart! Eur J Pediatr Surg. 2007;17:214-216. Grisoni ER, Gauderer MWL, Wolfson RN, Jassani MN, Olsen MM. Antenatal diagnosis of sacrococcygeal teratomas: prognostic features. Pediatr Surg Int. 1988;3:173-175. Grosfeld JL, Ballantine TVN, Lowe D, et al. Benign and malignant teratomas in children: analysis of 85 patients. Surgery. 1976;80: 297-305. Gross RE, Clatworthy HW, Meeker IA. Sacrococcygeal teratomas in infants and children. Surg Gynecol Obstet. 1951;92:341-354. Gross SJ, Benzie RJ, Sermer M, Skidmore MB, Wilson SR. Sacrococcygeal teratoma: prenatal diagnosis and management. Am J Obstet Gynecol. 1987;156:393-396. Gruenwald P. Tissue anomalies of probable neural crest origin in a twenty millimeter human embryo with myeloschysis. Arch Pathol. 1941;31:489-500. Hawkins E, Issacs H, Cushing B, et al. Occult malignancy in neonatal sacrococcygeal teratomas. A report from a Combined Pediatric Oncology Group and Children’s Cancer Group study. Am J Pediatr Hematol Oncol. 1993;15:406-409. Hedrick HL, Flake AW, Crombleholme TM, et al. Sacrococcygeal teratoma: prenatal assessment, fetal intervention, and outcome. J Pediatr Surg. 2004;39:430-438. Heerema-McKenney A, Harrison MR, Bratton B, et al. Congenital teratoma: a clinicopathologic study of 22 fetal and neonatal tumors. Am J Surg Pathol. 2005;29:29-38. Heifetz SA, Cushing B, Giller R, et al. Immature teratomas in children: pathologic considerations: a report from the combined Pediatric Oncology Group/Children’s Cancer Group. Am J Surg Pathol. 1998;22:1115-1124. Heys RF, Murray CP, Kohler HG. Obstructed labour due to foetal tumours: cervical and coccygeal teratoma. Gynaecologia. 1967;164:43-54. Hickey RC, Layton JM. Sacrococcygeal teratoma: emphasis on the biological history and early therapy. Cancer. 1954;7:103l-1043. Hickey RC, Martin RG. Sacrococcygeal teratomas. Ann NY Acad Sci. 1964;114:951-957. Hogge WA, Thiagarajah S, Barber VG, Rodgers BM, Newman BM. Cystic sacrococcygeal teratoma: ultrasound diagnosis and perinatal management. J Ultrasound Med. 1987;6:707-710. Holzgreve W, Flake AW, Langer JC. The fetus with sacrococcygeal teratoma. In: Harrison MR, Golbus MS, Filly RA, eds. The Unborn Patient. Philadelphia: WB Saunders; 1991:461. Holzgreve W, Mahony BS, Glick PL, et al. Sonographic demonstration of fetal sacrococcygeal teratoma. Prenat Diagn. 1985;5:245-257. Holzgreve W, Miny P, Anderson R, Golbus MS. Experience with 8 cases of prenatally diagnosed sacrococcygeal teratomas. Fetal Ther. 1987;2:88-94. Horger E, McCarter LM. Prenatal diagnosis of sacrococcygeal teratoma. Am J Obstet Gynecol. 1979;134:228-229. Huddart SN, Mann JR, Robinson K, et al. Sacrococcygeal teratomas: the UK Children’s Cancer Study Group’s experience. Pediatr Surg Int. 2003;19:47-51. Hunt PT, Kendrick CD, Ashcraft KW, et al. Radiography of hereditary presacral teratoma. Radiology. 1977;122:187-191. Ibrahim D, Ho E, Scherl SA, et al. Newborn with an open posterior hip dislocation and sciatic nerve injury after intrauterine radiofrequency ablation of a sacrococcygeal teratoma. J Pediatr Surg. 2003;38:248-250. Izant RJ Jr, Filston HC. Sacrococcygeal teratomas: analysis of forty-three cases. Am J Surg. 1975;130:617-621. Johnson JWC, Porter J, Kellner KR, et al. Abdominal rescue after incomplete delivery secondary to large fetal sacrococcygeal teratoma. Obstet Gynecol. 1988;71:981-983. Jouannic JM, Dommergues M, Auber F, et al. Successful intrauterine shunting of a sacrococcygeal teratoma (SCT) causing fetal bladder obstruction. Prenat Diagn. 2001;21:824-826. Kapoor R, Saha MM. Antenatal sonographic diagnosis of fetal sacrococcygeal teratoma with hydrops. Australas Radiol. 1989;33:285-287. Kay S, Khalife S, Laberge JM, et al. Prenatal percutaneous needle drainage of cystic sacrococcygeal teratomas. J Pediatr Surg. 1999;34:1148-1151. Kirk D, Lister J. Urinary complications of sacrococcygeal teratoma. Z Kinderchir. 1976;18:294-304. Kirkinen P, et al. Ultrasonic and magnetic resonance imaging of fetal sacrococcygeal teratoma. Acta Obstet Gynecol Scand 76, 917-922 (1997). Kowalski E, Sokolowska-Pituchowa J. Teratoma of the fetal sacral as a delivery obstacle. Ginekol Pol. 1968;39:123-124. (English summary.) Kuhlmann RS, Warsof SL, Levy DL, Flake AJ, Harrison MR. Fetal sacrococcygeal teratoma. Fetal Ther. 1987;1:95-100. Lahdenne P, Wikstrom˜ S, Heinheimo M, et al. Late urological sequelae after surgery for congenital sacrococcygeal teratoma. Pediatr Surg Int. 1992;7:195-198. Lam YH, Tang MH, Shek TW. Thermocoagulation of fetal sacrococcygeal teratoma. Prenat Diagn. 2002;22:99-101. Langer JC, Harrison MR, Schmidt KG, et al. Fetal hydrops and death from sacrococcygeal teratoma: rationale for fetal surgery. Am J Obstet Gynecol. 1989;160:1145-1150. Le LD, Alam S, Lim FY, Keswani SG, Crombleholme TM. Prenatal and postnatal urologic complications of sacrococcygeal teratomas. J Pediatr Surg. 46(6), 1186-1190 (2011). Le Caignec C, Winer N, Boceno M, et al. Prenatal diagnosis of sacrococcygeal teratoma with constitutional partial monosomy 7q/trisomy 2p. Prenat Diagn. 2003;23:981-984. Lemire RJ, Beckwith JB. Pathogenesis of congenital tumors and malformations in the sacrococcygeal region. Teratology. 1982;25:201-213. Linder D, Hecht F, McCaw BK, et al. Origin of extragonadal teratoma and endodumal sinus tumors. Nature. 1975;254:597-600. Litwiller MR. Dystocia caused by sacrococcygeal teratomas. Obstet Gynecol. 1969;34:783-786. Lowenstein A, Schwartz H, Simon SR, Roth E, Scheininger LM. Delivery of a fetus with a large sacrococcygeal tumor, an unusual case. J Newark Beth Isr Hosp. 1963;14:78-84. Lu T, Lee KH. Two cases of congenital sacral teratoma obstructing labour. J Obstet Gynaecol Br Commonw. 1966;73:852-854. Mahour GH, Woolley MM, Trinedi SN, et al. Sacrococcygeal teratoma: a 33-year experience. J Pediatr Surg. 1975;10:183-188. Malone PS, Kiely EM, Brereton RJ, et al. The functional sequelae of sacrococcygeal teratoma. J Pediatr Surg. 1990;25:679-680. Marina NM, Cushing B, Giller R, et al. Complete surgical excision is effective treatment for children with immature teratomas with or without malignant elements: A Pediatric Oncology Group/Children’s Cancer Group Intergroup Study. J Clin Oncol. 1999;17:2137-2143. Mintz MC, Mennuti M, Fishman J. Prenatal aspiration of sacrococcygeal teratoma. AJR Am J Roentgenol. 1983;141:367-368. Misra D, Pritchard J, Drake DP, et al. Markedly improved survival in malignant sacrococcygeal teratomas—16 years’ experience. Eur J Pediatr Surg. 1997;7:152-155. Musci MN, Clark MJ, Ayres RE, Finkel MA. Management of dystocia caused by a large sacrococcygeal teratoma. Obstet Gynecol. 1983;62:10S-12S. Nakoyama DK, Killion A, Hill LM, et al. The newborn with hydrops and sacrococcygeal teratoma. J Pediatr Surg. 1991;26:1435-1438. Nassenstein K, Schweiger B, Barkhausen J. Prenatal diagnosis of anasarca in an end-second trimester fetus presenting with sacrococcygeal teratoma by magnetic resonance imaging. Magn Reson Imaging. 2006;24:977-978. Nicolay KS, Gainey HL. Pseudotoxemic state associated with severe Rh isoimmunization. Am J Obstet Gynecol. 1964;89:41-45. Ohama K, Nagase H, Ogina K, et al. Alpha-fetoprotein levels in normal children. Eur J Pediatr Surg. 1997;7:267-269. Ozkan KU, Bauer SB, Khoshbin S, et al. Neurogenic bladder dysfunction after sacrococcygeal teratoma resection. J Urol. 2006;175: 292-296. Paek BW, Jennings RW, Harrison MR, et al. Radiofrequency ablation of human fetal sacrococcygeal teratoma. Am J Obstet Gynecol. 2001;184:503-507. Quinn TM, Hubbard AM, Adzick NS. Prenatal magnetic resonance imaging enhances fetal diagnosis. J Pediatr Surg. 1998;33:553-558. Rescorla FJ, Sawin RS, Coran AG, et al. Long-term outcome for infants and children with sacrococcygeal teratoma: a report from the Childrens Cancer Group. J Pediatr Surg. 1998;33:171-176. Robertson FR, Crombleholme TM, Frantz ID III, et al. Devascularization and staged resection of giant SCT in the preterm infant. J Pediatr Surg. 1995;30:309-311. Roman AS, Monteagudo A, Timor-Tritsch I, et al. First-trimester diagnosis of sacrococcygeal teratoma: the role of three-dimensional ultrasound. Ultrasound Obstet Gynecol. 2004;23:612-614. Schey WL, Shkolnik A, White H. Clinical and radiographic considera-tions of sacrococcygeal teratomas: an analysis of 26 new cases and review of the literature. Radiology. 1977;125:189-195. Schiffer MA, Greenberg E. Sacrococcygeal teratoma in labor and the newborn. Am J Obstet Gynecol. 1956;72:1054-1062. Schmidt KG, Silverman NH, Harrison MR, Callen PW. High-output cardiac failure in fetuses with large SCT: diagnosis by echocardiography and Doppler ultrasound. J Pediatr. 1989;114:1023-1028. Sciaky-Tamir Y, Cohen SM, Hochner-Celnikier D, et al. Three-dimensional power Doppler (3DPD) ultrasound in the diagnosis and follow-up of fetal vascular anomalies. Obstet Gynecol. 2006;194:274-281. Sebire NJ, Fowler D, Ramsay AD. Sacrococcygeal tumors in infancy and childhood: a retrospective histopathological review of 85 cases. Fetal Pediatr Pathol. 2004;23:295-303. Seeds JW, Mittelstaedt CA, Cefalo RC, Parker TF. Prenatal diagnosis of sacrococcygeal teratoma: an anechoic caudal mass. J Clin Ultrasound. 1982;10:193-195. Seidenberg B, Hurwitt ES. Clinical aspects and management of sacrococcygeal teratoma. Arch Surg. 1958;76:429-436. Sheth S, Nussbaum AR, Sanders RC, et al. Prenatal diagnosis of sacrococcygeal teratomas: sonographic-pathologic correlation. Radiology. 1988;169:131-136. Smith B, Passaro E, Clatworthy HW. The vascular anatomy of sacrococcygeal teratomas: its significance in surgical management. Surgery. 1961;49:534-539. Sy ED, Lee H, Ball R, et al. Spontaneous rupture of fetal sacrococcygeal teratoma. Fetal Diagn Ther. 2006;21:424-427. Tanaka K, Kanai M, Yosizawa J, et al. A case of neonatal neuroblastoma mimicking Altman type III sacrococcygeal teratoma. J Pediatr Surg. 2005;40:578-580. Tanaree P. Delivery obstructed by sacrococcygeal teratoma. Am J Obstet Gynecol. 1982;142:239. Tapper D, Lack EE. Teratomas in infancy and childhood: a 54 year experience at the Children Hospital Medical Centre. Ann Surg. 1983;198:398-410. Theiss EA, Ashley DJB, Mostofi FK. Nuclear sex of testicular tumors and some related ovarian and extragonadal neoplasms. Cancer. 1960;13:323-330. Tsuchilda Y, Urano Y, Endo Y, et al. A study on alphafetoprotein and endodermal sinus tumor. J Pediatr Surg. 1975;10:501-506. Valdiserri RO, Yunis EJ. Sacrococcygeal teratomas: a review of 68 cases. Cancer. 1981;48:217-221. Varga DA, Kaplan RF, Kellner KR, Johnson JW, Miller D. Vaginal delivery impeded by a large sacrococcygeal teratoma: anesthetic considerations. Anesth Analg. 1987;66:1325-1327. Waldhausen JA, Kilman JW, Vellios F, Battersby JS. Sacrococcygeal teratoma. Pediatr Surg. 1963;54:933-949. Wax JR, Benn P, Steinfeld JD, et al. Prenatally diagnosed sacrococcygeal teratoma: a unique expression of trisomy 1q. Cancer Genet Cytogenet. 2000;117:84-86. Weiss DB, Wajntraub G, Abulafia Y, Schiller M. Vaginal surgical intervention for a sacrococcygeal teratoma obstructing labor. Acta Obstet Gynecol Scand. 1976;55:183-185. Werb P, Scurry J, Ostor A, Fortune D, Attwood H. Survey of congenital tumors in perinatal necropsies. Pathology. 1992;24:247-253. Werner B, Swiecicka K. Teratoma of the sacrococcygeal region of the fetus resulting as a delivery obstacle. Ginekol Pol. 1968;39:925-927. (English summary.) Wilson CA, Litton C, Capinpin A. Sacrococcygeal teratoma associated with congenital spinal deformity. Plast Reconstr Surg. 1963;31:289-293. Wooley MM. Teratomas. In: Ashcraft KW, Holder TM, eds. Pediatric Surgery. 2nd ed. Philadelphia: WB Saunders; 1993:47-862. Yadav DK, et al. Sacrococcygeal Teratoma: Clinical Characteristics, Management, and Long-term Outcomes in a Prospective Study from a Tertiary Care Center. JIAPS. 25(1), 15-21 (2020). Yoon SH, Park SH. A case of type III cystic sacrococcygeal teratoma. Pediatr Neurosurg. 2006;42:234-236. Zaccara A, Iacobelli BD, Adorisio O, et al. Gait analysis in patients operated on for sacrococcygeal teratoma. J Pediatr Surg. 2004;39: 947-952.