Ependymoma of the ovary. A case report with immunohistochemical, ultrastructural, and DNA cytometric findings, as well as histogenetic considerations.

Ovarian and paraovarian ependymomas are rare. This report presents the case of a 68-year-old woman with a stage Ia ependymoma of the ovary. The histologic picture was similar to that of ependymomas of the central nervous system. Immunohistochemical, electron microscopic, and DNA flow cytometric studies were performed from formalin-fixed, paraffin-embedded tissue. The diagnosis was supported by positive staining of cytoplasmic processes for glial fibrillary acidic protein. Immunoreactivity for vimentin, neuron-specific enolase, S-100, epithelial membrane antigen, and cytokeratin was also demonstrated. Ultrastructural examination revealed the presence of cilia on the surface of cysts and within intracellular lumina, abundant intermediate filaments in cytoplasmic processes, and intercellular junctions. The tumor displayed a diploid DNA content by flow cytometry. The histogenesis of ovarian ependymomas is uncertain but may include an origin from a preexisting ovarian teratoma or neometaplasia of müllerian duct-derived tissue.