A female infant born with a large sacrococcygeal mass underwent incomplete excision at 3 weeks of age. She returns at 14 months with a recurrent pelvic mass. Biopsy confirms malignant transformation. Which feature of sacrococcygeal teratoma best explains this outcome?

• A Malignant change depends entirely on maternal alpha-fetoprotein levels at birth
• B All sacrococcygeal teratomas metastasize to lung within the first year unless irradiated
• C Risk of malignant change rises sharply after 2 months of age and is higher with residual coccyx or incomplete excision ✓
• D Recurrence is inevitable because the tumor always infiltrates the sacral nerve roots

Explanation

Sacrococcygeal teratoma is the most common neonatal tumor. In the newborn period it is usually mature and benign, but after about 2 months of age the proportion of malignant yolk sac tumors rises steeply. Complete resection must include the coccyx, because remnants of coccygeal tissue harbor recurrence and malignant potential. Serum alpha-fetoprotein is used for follow-up after surgery, not as a determinant of malignant behavior, and the tumor is typically well encapsulated without sacral nerve infiltration in infancy.

Reference: Pediatric Surgery NaT, American Pediatric Surgical Association ed.

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Written and medically reviewed by the StethoPrep medical team.