Progressive angiomyolipoma with inferior vena cava tumor thrombus.

A 45-year-old man presented with an incidentally discovered benign renal angiomyolipoma. This lesion initially demonstrated renal vein involvement. On referral to our institution 3 years later, there was interval progression of tumor thrombus to the intrahepatic inferior vena cava. Intravascular extension of benign angiomyolipoma, though rare, has been reported. We present a new example and review the literature concerning this unusual complication of a common renal neoplasm.