Stromal Endocrine Cell Micronests Associated With an Ovarian Mucinous Cystadenoma: Endocrine Cell Preservation (Pseudohyperplasia) Potentially Mimicking Stromal Sex Cord Proliferation or Tumor Microinvasion

Endocrine cell micronests (ECMs) have been described only twice previously in the ovary, both in association with mucinous neoplasms exhibiting intraepithelial endocrine cell hyperplasia. We report a 31-yr-old patient with a mucinous cystadenoma in which ECMs were distributed in the stroma surrounding degenerate glandular elements. Immunohistochemistry demonstrated only sparse endocrine cells within the neoplastic glands. We postulate that the ECMs in this case reflected relative preservation of endocrine elements in the context of epithelial atrophy, a process more commonly encountered in gastrointestinal pathology. Ovarian ECMs should also be distinguished from stromal sex cord proliferations and tumor microinvasion.