Paratesticular endometriosis in a man with a prolonged hormonal therapy for prostatic carcinoma

A rare case of paratesticular endometriosis in a 69-year-old male with prostatic carcinoma, who had a history of 9-year hormonal therapy, is presented. The lesion was a multilocular cyst, 5.2 cm × 3.1 cm × 3.0 cm in size, in the left paratestis. The cysts were lined by a single layer of cuboidal cells. A small number of glands were scattered in the underling stroma composed of closely packed small round or ovoid cells with scant cytoplasm resembling endometrial stromal cells, and abundant capillaries. Hemosiderin deposits were observed. Immunohistochemically, the lining cells of the cysts and glands were positive for CAM5.2, vimentin and calretinin, and were negative for CD10, estrogen and progesterone-receptors, indicating mesothelial profiles. The stromal cells expressed vimentin, estrogen- and progesterone-receptors and CD10. The findings indicated stromal endometriosis associated with the tunica vaginalis. Mullerian or endometriotic metaplasia and stromal cell hyperplasia under the influence of prolonged estrogen therapy may be the mechanism of this lesion.