Sacrococcygeal Teratoma
A teratoma is generally defined as a tumor arising from pleuripotent cells, composed of a wide variety of tissues haphazardly arranged, usually representing derivatives of their germ layers. Sacrococcygeal teratoma (SCT) is usually obvious at birth, presenting as a large exophytic mass with solid or cystic or mixed components in the sacrococcygeal region. SCT may be classified into four types as follows:
- Type I: nearly entirely external Fig 1
- Type II: internal and external in equal proportions Fig 2
- Type III: mainly internal Fig 3
- Type IV: entirely internal with no external component. Fig 4
Fig 1: Schematic drawing of SCT type I: predominantly external component
Fig 2: Schematic drawing of SCT type II: predominantly external component with significant intrapelvic component
Fig 3: Schematic drawing of SCT type III: predominantly internal component with intra-abdominal extension
Fig 4: Schematic drawing of SCT type IV: entirely internal component
Moreover, they are histologically categorized into three main groups, including benign (75%), malignant (13%) and immature (12%).
Incidence: SCT is a rare tumor, but the most common fetal tumor, with an incidence of 1:20,000-1:40,000 live births. The male to female ratio is 1:3-4. Most cases are sporadic, but familial presacral teratomas have been reported.
Sonographic findings:
Fig 5, Fig 6, Fig 7, Fig 8, Fig 9, Fig 10, Fig 11
- The teratomas exhibited three sonographic patterns: mixtures of cystic and solid components in equal proportions, predominantly solid with a few scattered anechoic areas, and unilocular cystic masses. The majority of SCTs are solid or mixed cystic and solid, and only 15% are entirely cystic.
- Anterior displacement of the bladder in cases of intra-abdominal components.
- The main differential diagnosis includes
- anterior or posterior meningomyeloceles
- conjoined twins, especially with large tumors
- hemangioma
- neuroectodermal cyst.
- The entirely intra-abdominal cystic mass must be distinguished from ovarian cyst, meconium pseudocyst or enteric duplication cyst.
- Evidence of high-output heart failure, placentomegaly, polyhydramnios, or hydrops fetalis is often seen in large tumors. Doppler echocardiography to detect the presence of congestive heart failure may allow well-timed therapeutic interventions.
- Umbilical artery waveform or reversed diastolic flow suggest impending fetal demise.
- Serial ultrasound examinations should be performed to assess amniotic fluid volume, tumor growth, fetal well-being, and early evidence of hydrops.
- Visualization of an intra-abdominal component, including pelvic structures and vasculature demonstrated with 3D ultrasound, is of prognostic importance. However, there was no correlation between the sonographic appearance and the presence of immature or malignant components.
- Usually diagnosed in the second and third trimesters.
Fig 5: Sacrococcygeal teratoma Sagittal scan of the spine (21 weeks): abnormal complex solid mass with heterogeneous echodensity (*) located at the end of sacrum
Fig 6: Sacrococcygeal teratoma Sagittal scan of the spine (29 weeks): abnormal complex solid mass with heterogeneous echodensity (*) located at the end of sacrum
Fig 7: Sacrococcygeal teratoma Sagittal scan of the spine (27 weeks): abnormal complex solid mass with heterogeneous echodensity (*) located at the end of sacrum
Fig 8: Sacrococcygeal teratoma Sagittal scan of the spine (26 weeks): abnormal complex solid mass with heterogeneous echodensity (*) located at the end of sacrum
Fig 9: Sacrococcygeal teratoma Sagittal scan of the spine (35 weeks): bizarre complex solid mass with heterogeneous echodensity (*) located at the end of sacrum (arrow) and complicated with ascites
Fig 10: Sacrococcygeal teratoma Cross-sectional scan of the lower spine (17 weeks): cystic mass (*) located between bladder (solid circle) and sacrum
Fig 11: Sacrococcygeal teratoma Sagittal scan of the lower spine (29 weeks): cystic mass (*) located at the end of sacrum (arrow)
Video clips of sacrococcygeal teratoma
Sacrococcygeal Teratoma : Mass on the back: the complex cyst at the caudal end of the spine
Associations: Musculoskeletal abnormalities (most common), and renal, cardiovascular, gastrointestinal and CNS anomalies (less common).
Management: The fetuses with a large tumor should be delivered by cesarean section to avoid dystocia and catastrophic hemorrhage during delivery. Small teratomas as well as most cystic tumors allow vaginal delivery after having been punctured previously. Fetal surgical intervention, such as resection, radiofrequency ablation, thermocoagulation, intrauterine shunting in the case of bladder obstruction or percutaneous drainage or aspiration of the cystic type, has proven successful in highly selected cases.
Prognosis: Hydrops fetalis, premature delivery, type III and IV, diagnosis at an earlier gestational age predicts a poor outcome. Types I and II with appropriate surgical correction are related to a better prognosis.