Tumor imprint cytology of ovarian ependymoma. A case report

Background: Ependymoma is a tumor that usually develops in the central nervous system and is extremely rare in the ovary. The first case of ovarian ependymoma was reported by Kleinman et al. (Kleinman GM, Young RH, Scully RE. Ependymoma of the ovary: report of three cases. Hum Pathol 1984;15:632-8.) in 1984, and only eight cases have been reported since then. Criteria for the histopathologic diagnosis of ependymoma are already established, but there has been no investigation of the cytologic diagnosis of ovarian ependymoma.

Methods: An imprint cytologic specimen was obtained from a recurrent ovarian ependymoma. The imprint cytologic features were compared with the findings of histologic examination, immunostaining, and electron microscopy.

Results: Imprint cytology revealed clusters of small cells with tapering cytoplasmic processes and a round nucleus. On the basis of these features, a neurogenic tumor could be included in the differential diagnosis. Furthermore, many rosette-like collections of cells that were suggestive of ependymal rosettes or perivascular pseudorosettes, characteristic of ependymoma, were found. The presence of ependymal rosettes and perivascular pseudorosettes also were confirmed by the histopathologic examination. Together with positive immunostaining for glial fibrillary acidic protein, this led to the diagnosis of ependymoma, which also was supported by the electron microscopic findings.

Conclusions: Careful observation of the imprint cytologic specimen of an ovarian ependymoma should reveal numerous rosette-like collections of cells that were suggestive of ependymal rosettes or perivascular pseudorosettes. In addition, if we remember that ependymoma can develop in the ovary and find cells with tapering processes that suggest a neurogenic tumor, it may be possible to detect histologic features characteristic of ependymoma by the imprint cytology. To our knowledge, this is the first report on the imprint cytologic diagnosis of ependymoma originating in the ovary.