Monotypic epithelioid angiomyolipoma of the kidney: a case report

A case of monotypic variant of epithelioid angiomyolipoma (AML) observed in a 62-year old woman is reported. The patient complained of abdominal fullness caused by a huge left renal mass without evidence of tuberous sclerosis complex. Imaging studies showed a left renal mass with an area showing hemorrhage and necrosis. The left renal mass, spleen and pancreatic tail were removed en bloc transabdominally. The resected tumor weighed 1200 g and showed focal necrosis and hemorrhage. Microscopically, the tumor was composed exclusively of atypical polygonal cells with copious eosinophilic cytoplasm, pleomorphic nuclei and prominent nucleoli. Tumor cells were considered to derive from perivascular epithelioid cells, and exhibited strong positive staining for HMB-45 and c-KIT, but were negative for epithelial, smooth muscle, and neural markers. As this tumor had none of the typical elements of classic AML, the final pathological diagnosis was monotypic epithelioid AML.