'Minimal deviation' endometrioid carcinoma with oncocytic change of the endometrium.

We report an unusual adenocarcinoma of the endometrium in an 80-year-old woman. The tumor diffusely involved the entire thickness of the myometrium. The cervix, ovaries, and fallopian tubes were unremarkable. Microscopic examination revealed an extremely well-differentiated endometrioid adenocarcinoma with mild cytologic atypia and slightly distorted glands infiltrating almost the entire thickness of the myometrium. In addition, the neoplastic endometrioid cells showed extensive oncocytic change. Endometrial curettings had been interpreted as simple endometrial hyperplasia with eosinophilic metaplasia. The significance of this lesion is discussed in terms of possible confusion with benign endometrial lesions as well as benign cervical lesions.