What Is a Fetal Sacrococcygeal Teratoma?
Fetal sacrococcygeal teratomas are uncommon tumors in the sacrococcygeal region (at the tailbone (coccyx) region). The tumor is usually non-cancerous (benign) and congenital (present at birth). In some rare cases, the tumor is cancerous (malignant); the tumor can also become cancerous if surgical removal is not done. Most tumors are slow growing and develop prenatally. It is mostly found in routine prenatal ultrasound examinations.
The actual cause is unknown. The condition is more prevalent in females than males, but malignancies associated with the condition are more prevalent in males. The condition's prevalence is 1 in every 30,000 to 70,000 live births. It is the commonest solid tumor found in neonates. They are uncommon in adults, and those found in adults are mostly undetected tumors present at the time of birth.
What Are the Causes?
The actual cause is not known. Teratomas are germ cell tumors, and sacrococcygeal teratomas are neonates' most common. Germ cells are present in the embryonic stage and later develop into the reproductive system. Germ cell tumors mostly develop in the ovaries, testes, or lower back. If germ cell tumors develop outside the gonad, they are called extragonadal tumors. Some studies show that germ cell migration during embryogenesis is responsible for tumor development.
What Are the Signs and Symptoms?
Symptoms vary depending on the location and size of the tumor. Small tumors are usually asymptomatic and are removed surgically. On the other hand, large tumors result in complications both prenatally and after birth.
The symptoms include:
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Fetal heart failure.
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Fluid accumulation in the skin and body cavity, a condition called hydrops.
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Ascites.
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Fetuses below 30 weeks rarely survive hydrops.
If untreated, hydrops can result in maternal mirror syndrome complications in the mother.
These include:
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Swelling.
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Vomiting.
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Protein in urine.
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Fluid in lungs.
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Shortness of breath.
Hydrops occur in about 15 % of large fetal sacrococcygeal teratomas.
Some cases of the tumor present with the following symptoms:
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Polyhydramnios (a large amount of amniotic fluid).
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Bleeding into the tumor.
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Tumor rupture.
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Bleeding into amniotic space.
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Fetal urinary obstruction.
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Dystocia (obstructed labor due to large tumor size).
Sacrococcygeal teratomas are mostly asymptomatic in adults.
In some cases, the following symptoms are present:
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Fatigue.
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Lower back pain.
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Urinary tract infection.
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Constipation.
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Increased frequency of stools.
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Numbness.
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Partial paralysis of legs.
Based on the location of the tumor, they are classified as follows:
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Type Ⅰ- Most of the tumor is located outside the body and is attached to the tailbone.
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Type Ⅱ- Tumor located externally with a significant intrapelvic portion.
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Type Ⅲ- Tumors are mostly located inside the body (intrapelvic region) but can be seen from outside too.
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Type Ⅳ- Tumors located fully inside the body without an external component.
How Is the Condition Diagnosed?
A high level of alpha-fetoprotein in the mother’s blood indicates the presence of a tumor. If the tumor is situated outside the fetal body, it gets diagnosed during a routine ultrasonic examination in the second trimester of pregnancy.
Other diagnostic examinations done include:
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Doppler Ultrasound - Used for measuring blood flow to the tumor.
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Fetal Echocardiogram- Make use of sound waves for checking the fetal heart.
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Fetal MRI (Magnetic Resonance Imaging)- A non-invasive imaging procedure used to get a detailed view of the tumor.
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Amniocentesis - A small amount of amniotic fluid is taken and examined for genetic abnormalities.
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Biopsy- Microscopic examination of the affected tissue helps in confirming the diagnosis. In the fine needle aspiration technique, a hollow needle is inserted through the skin into the nodules, and a small tissue mass is taken.
In some cases, the condition is diagnosed only after birth. If the tumor is present externally, it gets diagnosed on physical examination. If the tumor is fully located inside the body, the diagnosis may be delayed, and get diagnosed with the appearance of symptoms like urinary obstruction, lower back pain, etc.
How Is the Condition Managed?
In all cases where the fetus has a large sacrococcygeal tumor, a cesarean section is done to avoid tumor rupture and tumor hemorrhage during delivery. Most such babies are born prematurely and require expert perinatal care. Managing the condition requires a multidisciplinary approach with an expert perinatal care team.
The treatment options include:
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Surgical Resection:
Surgical resection involves the removal of the tumor along with the coccyx; failure to remove the coccyx is associated with a local recurrence rate of 30%. In cases where the tumor extends into the abdomen, an abdominal incision is required. Early resection of the tumor is associated with a low recurrence rate. A follow-up visit is done under the supervision of a pediatric surgeon three years after the surgery.
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Fetal Surgery:
Fetal surgery is performed in cases where the condition is life-threatening for the fetus.
The fetal surgical options include:
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Open Fetal Surgery- The condition is done under general anesthesia, an incision is made on the mother’s abdomen and uterus, and the tumor is reduced in size. It is used for the treatment of heart failure.
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Laser Ablation- The surgeon inserts a needle into the mother’s uterus and uses laser energy to destroy the blood vessels. After tumor removal, the fetus is returned to the womb.
What Is the Differential Diagnosis?
Conditions with symptoms similar to sacrococcygeal tumors include the following:
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Myelomeningocele:
Myelomeningocele is a birth defect due to improper spinal canal closure, resulting in a protrusion in the back region.
Symptoms depend on the location of the defect and include:
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Loss of bladder control.
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Loss of sensation.
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Loss of bowel control.
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Leg paralysis.
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Chordoma:
Chordomas are uncommon primary bone tumors that develop along the axis of the spine. Symptoms depend on the location. They may develop in the vertebral region, the sacrococcygeal region, or the skull base region.
Conclusion
Fetal sacrococcygeal teratomas are uncommon benign (mostly) tumors that develop at the base of the spine and are found in neonates. Small tumors are usually asymptomatic, but large ones present with complications like hydrops. If large ones are detected prenatally, fetal surgery may be done. The condition is mostly managed with surgical resection followed by follow-up visits.
