Non-hormone-induced mixed epithelial and stromal tumor of kidney in a man: description of a rare case.

Mixed epithelial and stromal tumor of the kidney is a recently recognized category of lesions occurring mostly in adult, middle-age women with a history of hormonal treatment. We present a rare case of a 58-year-old asymptomatic man without a history of hormonal treatment with a tumor characterized by proliferation of multiple cysts lined by single layers of epithelial cells and hypercellular stroma of spindle "ovarian-like" cells. Immunohistochemically, the stromal cells reacted against estrogen and progesterone receptors, vimentin, desmin, and CD34. A follow-up computed tomography scan performed 8 months after surgical enucleation of the lesion showed no signs of recurrence.