Sacroccygeal teratoma (SCT) is the most common type of tumor in the newborn, occurring in one in every 35,000 live births.
SCT diagnosed in the neonatal period is less likely to be malignant and has a favorable prognosis after resection. However, an utero fetal SCT can grow at unpredictable rates and to very large dimensions. This growth can lead to vascular steal, resulting in high-output cardiac failure, fetal hydrops and placentomegally. Mass effect from these tumors can also result in obstructive uropathy and significant renal damage.
SCT can present as a cystic (fluid filled) or solid mass or a combination of both, which is the most common type. There are four classifications of SCT according to the amount of tumor outside the body.
- Type I teratomas are completely external; the mass is outside the body.
- Type II teratomas have internal and external components. The internal portion is confined to the pelvic region.
- Type III teratomas have been internal and external components with the internal portion spreading to the abdominal area.
- Type IV teratomas are completely internal.
SCT can be diagnosed with a prenatal ultrasound. The ultrasound will show a mass in the area of the coccyx that may range in size. Other findings may include polyhydramnios or a uterus that is larger than normal for gestational age. Serial ultrasounds are done throughout the pregnancy to assess the fetal gestational age, the size and type of tumor, uterine size, amniotic fluid volume and fetal well-being. Measurements are taken to determine how far the teratoma extends into the abdomen and whether any organs are affected. A large teratoma can cause pressure on internal organs, especially the bladder, which can cause obstruction and kidney damage.
A predominately solid teratoma can contain a large amount of blood vessels, which can stress the fetal heart and require it to pump harder to circulate blood through the body. This may cause the fetus to develop hydrops, which is an abnormal accumulation of fluid from high-output cardiac failure.
Fetal echocardiograms throughout the pregnancy will monitor changes in cardiac output. A fetal MRI helps identify the type of SCT and any other structural anomalies. Pictured (right) is a fetal MRI indicating a Type I SCT that is largely cystic.
The delivery method is determined by the mass size and type. If the teratoma is small or largely internal, vaginal delivery may be an option. For larger or external masses, a cesarean section is required to avoid dystocia or rupture of the SCT, which can ultimately be life-threatening to the infant.
Following delivery, the SCT should be protected from injury with the use of non-adherent dressing. The newborn should be imaged to assess the anatomy, the extent of the internal component and operative planning. The SCT should then be resected, including the coccyx.
For fetuses that develop hydrops in utero, fetal intervention is indicated. This intervention can range from open fetal debulking of the mass to early delivery and debulking using the EXIT procedure. The approach depends on the gestational age and type of SCT.