Sacrococcygeal Teratoma

Introduction

Sacrococcygeal teratoma (SCT) is a rare tumor that forms at the base of a baby’s tailbone or other parts of the body. SCT develops from the same type of cells that form the reproductive tissues. When these cells develop abnormally, a tumor can result. 

This birth defect is more common in girls than in males. Although the tumors can grow very large, they are usually not malignant (cancerous). They can usually be cured with surgery after birth, but occasionally cause trouble before birth.

How Is SCT Diagnosed During Pregnancy?

A  can be detected through a routine ultrasound in the second trimester. It will appear as a mass near the bottom of the back. A screening blood test may detect abnormally high levels of maternal alpha-fetoprotein, which can also alert your physician that a SCT may be present.

After the initial ultrasound or blood test,  doctors or medical officers in teaching hospitals will perform an in-depth evaluation to determine the extent of the tumor. If a SCT is confirmed, we perform a targeted prenatal ultrasound and a fetal MRI to better examine the tumor and spine. Rarely, a small SCT may look like another birth defect called spina bifida. The MRI can help us make this distinction. Finally, we recommend a fetal echocardiogram. This specialized examination of the fetal heart will tell us how much strain is being put on the heart by the tumor.

SCT is typically discovered when a prenatal blood test at week 16 of pregnancy shows a high alpha fetoprotein (AFP) level, or when an ultrasound is performed because the uterus is abnormally large. The increased size of the uterus is often caused by extra amniotic fluid, called polyhydramnios.

Most newborns with SCT survive and do well with surgical removal of the tumor after birth. Malignant tumors are unusual. Rarely, fetuses with very large SCTs develop heart failure. These babies may be candidates for fetal intervention.

Fetuses with larger tumors or tumors that go up inside the baby's abdomen will require more complex surgery after birth, but generally do well. Very large tumors, which can reach the size of the fetus, can pose a difficult problem both before and after birth.

We have found that SCTs that are largely cystic — meaning filled with fluid — generally don't cause a problem. However, SCTs that are made up of mostly solid tissue and have a lot of blood flow can have adverse effects. This is because the fetus's heart has to pump blood to circulate not only to its body, but also to all the blood vessels of the tumor, which can be as big as the fetus. In essence, the heart is performing twice its normal amount of work.

Fetal echocardiography can be used to measure how hard the heart is working. If heart failure does develop — usually in cases with solid, rapidly growing tumors — the fetus usually will not survive without immediate intervention before birth.

Fetuses with large tumors that have a great deal of blood flow must be followed closely to watch for the development of heart failure, which can lead to fetal death. Even if heart failure does not develop, these babies may require caesarian section delivery and an extensive operation after birth. Most babies will do well once the tumor is completely removed.

The surgery can have long-term consequences, including the reoccurrence of the tumor or difficulty with urination. The child should undergo yearly blood tests for elevated alpha feto-protein (AFP) levels, and should be followed by an oncologist (cancer specialist) and pediatric surgeon in early childhood.