Angiomyolipoma with epithelial cysts of the kidney in a man

Angiomyolipoma (AML) is a well‐characterized tumor composed of vascular, smooth muscle and adipose elements. Recently, AML with epithelial cysts (AMLEC) has been described as a cystic variant of AML. Herein is reported an AMLEC in a 55‐year‐old man, and to the authors' knowledge this is the first case report of AMLEC in Japan. He was referred to hospital because of microhematuria. A left renal tumor was noted and partial nephrectomy was performed. Histology indicated that the tumor was composed of epithelial cysts, compact subepithelial stroma and muscle‐predominant AML. Immunohistochemically, the subepithelial compact stroma and muscle‐predominant AML were positive for HMB‐45, estrogen receptor (ER), progesterone receptor (PR), CD10, smooth‐muscle actin and desmin. Epithelial cysts were positive for pancytokeratin but negative for HMB‐45, ER and PR. This tumor was diagnosed as AMLEC, mainly based on the immunohistochemical result that subepithelial compact stroma and muscle‐predominant AML were positive for HMB‐45. The patient was alive with no evidence of recurrence at 2 years postoperatively. This case was very interesting because it suggests that AMLEC should enter into the differential diagnosis of adult renal neoplasms.