Ovarian prostatic tissue originating from hilar mesonephric rests

Nonteratoid prostatic differentiation in the ovary of a parous, phenotypica lly normal, postmenopausal woman is reported for the first time, to the aut hors' best knowledge. The patient was a 70-year-old woman who underwent bil ateral oophorectomy following pelvic ultrasound examination that showed enl argement of the left ovary and an equivocally abnormal Doppler signal. Hist ologic examination showed a normal right ovary and a left ovary enlarged by hilar cystic dilatation related to a proliferation of mesonephric remnants exhibiting various types of epithelial metaplasia, including hyperplastic rete and epididymal-like and clear cell epithelia resembling the lining of the seminal excretory system. These were closely associated, occasionally e ven merging, with a discrete area of prostatic acinar and smooth muscle dif ferentiation in the cyst wall. The identity of the prostatic tissue was con firmed immunohistochemically by positive staining with prostate specific an tigen and prostatic acid phosphatase. The lesion was associated with an inc idental, microscopic hemangioma. A developmental malformative origin of thi s abnormality cannot satisfactorily he explained by current embryologic con cepts. A hypothesis of a metaplastic induction of prostatic tissue by meson ephric remnants is proposed, since complex metaplastic changes coexisted wi thin the cysts and even showed epithelial transitions with the prostatic ac ini.