Cystic adenoma of the pigmented ciliary epithelium. Clinical, pathologic, and immunohistopathologic findings. A 51-year-old white man was found to have a deeply pigmented mass in the ciliary body and peripheral choroid of his right eye with an associated vitreous hemorrhage. Although the tumor appeared to be a ciliochoroidal melanoma, a melanocytoma and adenoma of the pigment epithelium also were considered in the differential diagnosis. The tumor was removed by a large partial lamellar sclerocyclochoroidectomy. Results of histopathologic evaluation showed a cystic adenoma of the pigmented ciliary epithelium. To the authors' knowledge, this was the first immunohistopathologic study of this tumor. Results of the study showed marked immunoreactivity for low molecular weight cytokeratins, vimentin, and S-100 protein. These immunohistochemical studies are consistent with the origin of this tumor from pigment epithelial cells. 