Adenomas of the rete ovarii.

This article reports the clinicopathological and immunohistochemical findings of two cases of adenoma of the the rete ovarii (RO), one unilateral and the other bilateral, presenting with atypical histological features in the right ovary. Both tumors were incidental findings in 62- and 64-year-old patients presenting with metrorrhagia. The predominantly cystic lesions measured 2 cm and 3 cm in diameter and microscopically, they were tubulopapillary proliferations of regular columnar cells with clear cytoplasm. The stroma showed extensive differentiation of polygonal, Leydig-like cells which was associated in both cases with simple endometrial hyperplasia. In both cases rete and hilar mesonephric remnants were found in the vicinity of the lesion. The atypical lesion in one case had a complex papillary proliferation different in pattern and cellularity from a retiform Sertoli-Leydig cell tumor. It showed extensive areas of eosinophilic change, pleomorphism, and a few mitoses but did not invade the adjacent ovarian stroma. Its stroma also had steroidally active cells. The patient was alive and well after a follow-up interval of 3 years. Immunohistochemically, the lesions were diffusely positive for CAM 5.2, vimentin, epithelial membrane antigen, OC 125, OC 125, and progesterone receptors.