Sacroccoygeal teratoma(SCT) is a tumor of neonates that arises from the tailbone or coccyx. It is the most common tumor of newborns, although it is quite rare occurring in approximately 1 in every 40,000 births. This birth defect is more common in females than in male newborns. Teratomas are types of tumors that have cells from all three germlines which means that SCTs can contain any type of tissue that exists in a human. They often have hair and bone and rudimentary tissues of multiple different organs. They can have malignant or cancerous elements which can only be determined after surgical resection.


SCT is usually diagnosed in utero by prenatal ultrasound. A mass, which may be solid, cystic or mixed, in the sacral/coccygeal region of the lower back is identified. Pregnancies with SCTs are carefully monitored throughout pregnancy. Worrisome signs on prenatal ultrasound and echocardiography are large size, solid masses, high blood flow, and growing size. The most worrisome sign is the presence of hydrops fetalis which happens as a result of heart failure when the tumor has enough blood flow that it strains the heart. Hydrops fetalis is seen on ultrasound by two or more of the following: fluid around the lungs, fluid around the heart, fluid in the abdomen, swelling of the skin, excess amniotic fluid (polyhydramnios) and swelling of the placenta (placentomegaly). Hydrops fetalis with SCT is uncommon but when it does happen, fetuses are highly unlikely to survive unless intervention is done. Fetal surgery can be performed and results in approximately survival of 50% of fetuses with SCT and hydrops. If the gestation is past 28-32 weeks, then early delivery can be considered with hydrops in order to perform surgical resection. Of note, when hydrops fetalis develops, the pregnant woman should be monitored for maternal mirror syndrome, wherein the pregnant woman mirrors the illness of the fetus and develops sings similar to preeclampsia with high blood pressure, protein in the urine and fluid retention.

In cases where no prenatal ultrasound is performed, the diagnosis is apparent from a mass arising from the sacrococcygeal region. It can often be quite large. If the mass is completely internal, then the diagnosis may be difficult and often delayed. Based on research at UCSF, delayed surgery for SCT may result in a higher rate of cancers seen in the SCT.

An MRI is performed after birth to see how large the internal portion of an SCT is. Additionally, alpha fetoprotein and beta Human chorionic gonadotrophin serum tests are sent as they can serve as tumor markers.


Most women who are pregnant with a baby with an SCT will require a cesarean section delivery. Some women with a small SCT may be able to delivery vaginally. After birth, babies will require treatment in an intensive care nursery. Successful surgical resection is the key to treatment for SCT. As these are rare and complex tumors, experience by the surgical team is critical to successful outcomes. Usually the surgery can be performed by excising the tumor from the back. Rarely when the tumor extends internally into the abdomen, an incision through the abdominal wall may be necessary to completely remove the tumor. Critical to long term success is removing the coccyx as this is the site where the tumor arises from.


One classification for SCT is the Altman classification which is determined by position in the body.

  • Altman class 1 are the most common and are SCTs that are predominantly external to the body.
  • Altman class 2 are the next most common SCTs and are mostly external with a significant internal component
  • Altman class 3 are mostly internal SCTs with a significant external component.
  • Altman class 4 are internal SCTs without a significant external component.

After surgical excision, SCTs are also categorized by their malignant potential.

  • Completely mature teratomas are benign.
  • Immature teratomas do not have evidence of cancer, but have an increased risk of the development of cancer.
  • SCTs can be noted to have cancerous elements within them although this is rare. These often will need chemotherapy in addition to surgery.


Long-term outcomes are generally quite good after surgical resection for SCT in the absence of malignant elements. For those patients with malignant elements, close followup with the surgical team and pediatric oncologists is necessary and chemotherapy is usually necessary.
Patients with SCT need to be followed up for recurrent tumor growth as well as bowel and bladder function as the SCT grows next to the bladder and the rectum, as well as the nerves that go to them.
Our team at UCSF is internationally recognized as leaders in SCT and has a followup program in our Long-term Infant to adult Followup and Evaluation(LIFE) clinic. This includes visits every 3 months for the first year of life, every 6 months for the second year of life and then yearly thereafter with assessment of bowel and bladder function, physical examination and checjking AFP and bHCG levels. We also perform MRIs at 18 months of age, 3 years of age and then again at 7 years of age. Our guidelines have been adopted by many centers across the world.