Ovarian microcystic stromal tumor: report of a new entity with immunohistochemical and ultrastructural studies.

Microcystic stromal tumor is a recently described rare subtype of ovarian tumor for which there has been no previously reported ultrastructural study. We report a case with the characteristic histological and immunohistochemical features and the first ultrastructural study. The immunohistochemical findings of strong and diffuse nuclear staining for beta catenin and P27 are suggestive of dysregulation of more than one genetic pathway. The ultrastructural findings are supportive of the previous postulation of an ovarian stromal origin of the neoplastic cells.