Oncocytoma of the caruncle.

Oncocytomas of the ocular adnexa are rare, but when they occur, are most commonly located on the caruncle. Oncocytic carcinomas have been reported but the majority of caruncular oncocytomas are benign. The lesions present as small, cystic, tan-to-red lesions. Histologically, the oncocytes are arranged in an adenomatous pattern. The cells have central nucleoli surrounded by eosinophilic cytoplasm. Electron microscopically, the cytoplasm is filled with mitochondria. As the packing of mitochondria increases, the nucleoli become eccentric and pyknotic, possibly suggesting an end-stage process. A typical clinical case is presented.