Retinal pigment epithelial carcinoma masquerading as choroidal melanoma—A rare case report

ABSTRACT Almost all retinal pigment epithelial (RPE) adenocarcinomas are clinically diagnosed as choroidal melanomas. Retinal adenoma and adenocarcinoma appear black in color. A 63-year-old woman presented with progressive visual loss in her right eye with intermittent throbbing pain. A brownish pigmented choroidal mass was identified occupying the entire intraocular cavity with hemorrhagic foci. Histopathology revealed an infiltrative epithelial neoplasm with ill-defined glandular differentiation and moderate cytological atypia. Immunohistochemical staining with epithelial membrane antigen, cytokeratin 7, HMB-45, and S-100 favored a RPE origin of the lesion. RPE adenocarcinoma is exceedingly uncommon, but should be included in the differential diagnosis of pigmented intraocular tumors. Histopathology, combined with immunohistochemistry, is essential for accurate diagnosis.