Metastatic renal epithelioid angiomyolipoma arising after a 23-year follow-up of sporadic renal angiomyolipoma

Epithelioid angiomyolipoma (EAML) is a rare variant of angiomyolipoma (AML) with potentially malignant characteristics such as local recurrence and distant metastasis. Although a component of EAML can be seen in typical AML, the biologic relationship between EAML and typical benign AML is not fully understood. We report a sporadic case of renal EAML that arose in a typical AML which was present for 23 years. A 74-year-old woman had been followed-up for AML in the right kidney with regular radiographic examinations for 21 years. After a 2-year interruption of evaluation, she visited the hospital again, complaining of right flank pain. Computed tomography revealed a rapidly growing solid tumor adjacent to the typical AML under surveillance. Histological examination of a radical nephrectomy specimen revealed that a fat-rich typical AML and EAML with nuclear atypia and mitosis composed 30 and 70 % of the tumor, respectively. Local recurrence and distant metastasis developed 3 months after surgical resection. The metastatic tumors grew rapidly despite chemotherapy with the MAID (mesna, adriamycin, ifosfamide, and dacarbazine) regimen, and she died 4 months after the surgery.