Oncocytoma-like angiomyolipoma. A clinicopathologic and immunohistochemical study of 2 cases.

We report the clinical, pathologic, and immunohistochemical features of an unusual tumor of the kidney composed of densely eosinophilic, polygonal epithelioid cells. The patients were a 56-year-old woman and a 35-year-old man. The renal tumors were discovered during follow-up for breast carcinoma and evaluation for abdominal pain, respectively. The tumors closely resembled oncocytoma in routine sections, but were negative for epithelial markers and positive for HMB-45, a pattern of reactions characteristic of angiomyolipoma. In the woman, a single additional microscopic angiomyolipoma was present in the renal parenchyma at a distance from the main tumor. Both patients are alive without recurrence 7 and 10 years after surgery, respectively. Based on clinical, morphologic, and immunophenotypic features, we conclude that these tumors are oncocytoma-like angiomyolipomas.