Cytopathologic findings in an immature cystic teratoma: report of an unusual case.

Teratomas are uncommon, usually benign tumors often found in young women. We describe the cytopathology of an unusual case of a large congenital teratoma in a 6-day-old girl. The patient initially showed signs of abdominal distention and a follow-up ultrasound and computerized-tomography (CT) revealed a cystic mass in the pelvis. An ultrasound-guided fine-needle aspiration (FNA) showed small round blue cells suspicious for a primitive neuronal tumor. Resection of the mass displayed a cystic teratoma with distinct nests of small round blue cells representing immature neuroepithelial and glial tissue. Also noted were admixed mature elements of a cystic teratoma. Cytologic finding of a small round blue cell tumor, therefore, was the immature component of the teratoma. This case illustrates the difficulties in diagnosing teratomas due to their extraordinary diversity.