Uteruslike masses of the ovary associated with breast cancer and raised serum CA 125

We describe three cases of a uteruslike mass of the ovary, a condition in which the ovary is replaced by a mass that grossly and microscopically resembles the uterus. The patients were 38, 43, and 39 years of age, and only the first was nulliparous. Two of them also had breast carcinomas. Two patients also had elevated CA 125 levels that gave rise to a clinical suspicion of ovarian malignancy. There were no anatomic abnormalities in any of the patients. The presence of residual ovarian stroma in two of the patients (both of whom had breast cancer) suggests that metaplasia rather than a congenital anomaly is the cause. Elevated CA 125 levels are consistent with the endomyometriosis nature of the lesion.