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What is a sacrococcygeal teratoma?

Sacrococcygeal teratoma (SCT) is a rare tumor that develops at the base of the spine near the tailbone (coccyx). SCTs are congenital, meaning they are present at birth and usually benign. SCTs appear in one in every 35,000 babies, making it the most common tumor found in newborns.

At Boston Children’s Hospital, our Maternal Fetal Care Center specializes in the evaluation and treatment of SCTs and other complex fetal conditions.

Sacrococcygeal Teratoma | Symptoms & Causes

What are the symptoms of a sacrococcygeal teratoma?

Sacrococcygeal teratomas usually don’t cause symptoms in pregnant people, but large SCTs can press on a fetus’ internal organs, like the bladder, causing kidney enlargement and blockage. Severe cases can also increase amniotic fluid levels, making the uterus bigger and causing discomfort, breathing issues, and early contractions for the pregnant person.

Another rare symptom of SCTs might be extra fluid in the fetus called hydrops. This can pose a threat to the fetus by blocking blood flow and affecting circulation, which in turn can increase the risk of swelling and high blood pressure in the pregnant person. These symptoms can be signs of conditions known as mirror syndrome or preeclampsia.

Sacrococcygeal Teratoma | Diagnosis & Treatments

How is a sacrococcygeal teratoma diagnosed?

A sacrococcygeal tumor is usually diagnosed during pregnancy by a highly specialized prenatal ultrasound or MRI. You may be referred to a doctor who specializes in fetal imaging if a routine prenatal scan or your alpha-fetoprotein (AFP) levels are concerning.

SCT types depend on their location, severity, and appearance:

  • Type I: Almost completely external (outside the fetus) and attached to the tailbone.
  • Type II: Mostly external, with a small part of the tumor growing inside the fetus.
  • Type III: Visible externally, but with the tumor extending from the pelvis into the abdomen.
  • Type IV: Completely internal.

SCTs can be either cystic (filled with liquid) or solid in appearance; they’re commonly a mixture of both.

A blood test to determine AFP levels (a protein produced by the developing fetus in the womb) is a routine part of prenatal care, and it’s usually done between the 15th and 20th week of pregnancy. It is one of several markers used to assess the health of the developing fetus and is expected to be increased in cases with SCT.

What other testing is done for sacrococcygeal teratomas?

  • Measurements will be taken to determine how far into the abdomen the SCT extends and what organs may have been affected.
  • Doctors will calculate the tumor-fetal ratio (TFR) to:
    • Assess the prognosis
    • Assess the likelihood of fluid buildup
    • Decide if fetal intervention is necessary. However, this is very uncommon.
  • Doctors will evaluate fetal blood flow patterns to assess fetal well-being and detect anemia.
  • Doctors usually recommend a fetal echocardiogram to assess the structure and function of the heart

How is a sacrococcygeal teratoma treated?

Treatment for SCTs requires surgery to remove the tumor. The timing of surgery depends on the diagnosis and severity of the tumor, but most often occurs within days of delivery. Surgery involves removing the tumor, along with the tailbone, and reconstructing the buttocks. Most babies recover completely after treatment, but your child’s surgeon will observe them for their first several years to monitor for bladder or bowel concerns and to ensure the tumor does not recur as even non-cancerous tumors can come back.

In rare cases when the removed tumor is malignant (cancerous), we work with the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center to create the best treatment plan for your child. Your child’s care team may determine that chemotherapy is necessary or no further treatment is needed.

Infrequently, the tumor can grow rapidly before birth and causes the fetus’ heart to pump extra hard to circulate blood through both its body and the tumor, possibly causing heart problems. In such situations, your doctor may suggest prenatal intervention.

Types of prenatal interventions

  • Intrauterine transfusion of blood products: Some cases of SCT are complicated by fetal anemia and thrombocytopenia (too few platelets) and may benefit from intrauterine transfusion of red blood cells and possibly platelets.
  • Ablation of feeding vessels: In this procedure, energy or coagulating materials are used to block the blood vessels that are supplying the tumor. When the tumor lacks blood flow, it can’t grow, reducing the fetus’ risk of heart failure. After birth, the tumor is removed in the operating room, and any necessary reconstruction is done.
  • Open fetal surgery: The uterus is opened, the fetus is partially taken out, and — while still attached to and sustained by the placenta — the tumor is dissected. Then, the fetus is placed back in the uterus, and the uterus is stitched up to continue the pregnancy as long as possible. Open fetal surgery is rarely indicated to treat SCT; it can lead to preterm labor and early delivery, and requires close monitoring after the procedure.

Reconstructive neonatal surgery may be necessary to properly close the perineum following surgery for a SCT. Fetal skin is remarkably resilient and may heal on its own without any scarring, depending on the development of the tumor’s cells.

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