Epithelioid Angiomyolipoma of Kidneys

Renal angiomyolipoma (AML) is a benign tumor composed of fat cells, smooth muscle cells, and thick-wall blood vessels. Epithelioid angiomyolipoma (EAML) is a variant of AML and is composed of purely epithelioid cell with melanogenesis markers. Neither adipocytes nor abnormal blood vessels are noted. Pathologically, tumor cells have nuclear atypia and eosinophilic cytoplasm. EAML has a malignant tendency and is difficult to differentiate from renal cell carcinoma (RCC). We report two cases in this study. The patients had no medical and family histories of tumor. The first patient, a 50year-old woman, had no symptoms and a renal tumor mass was noted incidentally in a healthy examination. Computer tomography of the abdomen showed a heterogeneous mass with slight calcification, and a blunt contour rising from the right kidney was noted. Initially RCC was diagnosed, thus this patient received a nephrectomy. The second patient, a 54-year-old woman, had left flank soreness and body weight loss of about 4 kgs over two months. Abdominal CT and ultrasound revealed a welldefined soft tissue lesion in the left retroperitoneal region and we suspected it from the left kidney. This patient received excision of the retroperitoneal tumor. Positive staining for HMB-45 (Human Melanoma Black-45) was noted in the pathological reports of both cases. EAML was the final diagnosis. Thus, we concluded EAML was required to confirm by pathology.