Ovarian ependymomas of extra-axial type or central immunophenotypes.

We report the differential clinicopathologic and immunophenotypical features of 2 pure ovarian ependymomas of extra-axial type with a predominant microcystic, anaplastic pattern occurring in patients aged 22 and 32 years and a unique myxopapillary pigmented ependymoma that originated within an ovarian mature cystic teratoma in a 35-year-old woman. The latter had a central nervous system phenotype different from that previously reported in ovarian ependymomas of extra-axial types, being negative for estrogen and progesterone receptors, epithelial membrane antigen and cytokeratin 34βE12, cell adhesion molecule 5.2, and cytokeratin 7. Furthermore, its benign behavior contrasted with the aggressive course of the other 2 ependymomas of extra-axial types, in which peritoneal invasion was present at the time of diagnosis. These findings illustrate that both central and extra-axial types of ependymoma show phenotypic variations that may point to either a derivation from different precursors or differentiation along diverse pathways. Thus, whereas ependymomas of extra-axial types would represent neometaplastic phenomena, those originated from the nervous tissue of teratomas resemble central nervous system ependymomas. Moreover, the dissimilarities between central and peripheral types of ependymoma would parallel the phenotypic differences present in primitive neural tumors of the female genital tract.