Immature teratoma of the ovary on fluid cytology.

A case of an immature teratoma of the ovary in the peritoneal fluid of a 10-yr-old girl who presented with a pelvic mass is presented and discussed. The ThinPrep preparation showed a few tight clusters of small tumor cells with a high nuclear/cytoplasmic ratio, round to oval nuclei with evenly distributed chromatin and one to two small distinct nucleoli, and scanty cytoplasm. The presence of immunohistochemical-confirmed glial tissue on the cell block preparation confirmed the diagnosis of an immature ovarian teratoma. The differential diagnosis of fluid cytology is discussed.