Ruptured Angiomyolipoma with Fatty Tumor Thrombus of the Renal Vein and Inferior Vena Cava

Renal angiomyolipoma is a benign clonal neoplasm that consists of three constituents, namely, blood vessels, adipose tissue and smooth muscle. Although renal angiomyolipoma has a benign nature and grows slowly, extrarenal occurrences have been reported in the hilar lymph nodes, retroperitoneum, liver, colon and direct extension to the renal vein and inferior vena cava as a tumor thrombus. Such a tumor thrombus is not an uncommon preoperative finding in renal cell carcinoma but is a rare presentation in renal angiomyolipoma. We present a case and review the literature, noting that tumor thrombus occur in sizable angiomyolipoma (> 4 cm), right kidneys and, predominantly, in females. The potentially lethal nature of a vena cava thrombus prompted radical surgery. (Chang Gung Med J 2006;29(4 Suppl):21-4)