Variants of renal angiomyolipoma closely simulating renal cell carcinoma: difficulties in the histological diagnosis.

Renal angiomyolipoma is considered to be a benign renal tumor composed of atypical blood vessels, smooth muscles and fat cells. We report 2 cases of unilateral renal angiomyolipoma. In both cases, our preoperative diagnosis was renal cell carcinoma, because no low density area compatible with fat tissue was noted in the tumors on radiographic evaluation. Through histological examination, both tumors proved to be angiomyolipomas mainly composed of epithelioid cells in 1 case, and spindle-shaped smooth muscle cells mimicking a leiomyoma in the other case. Both patients are well showing no evidence of metastases 16 and 14 months after nephrectomy, respectively. Copyright 2002 S. Karger AG, Basel