Angiomyolipoma is a benign renal neoplasm composed of fat, vascular, and smooth muscle elements. It has an incidence of about 0.3-3%, and 2 types are described: isolated angiomyolipoma and angiomyolipoma that is associated with tuberous sclerosis.

Isolated angiomyolipoma occurs sporadically, is often solitary, and accounts for 80% of the tumors. The mean patient age at presentation of isolated angiomyolipoma is 40 to 50 years, and this neoplasm is about 4 times more common in women than in men. Interestingly, 80% of the cases involve the right kidney.

Angiomyolipoma that is associated with tuberous sclerosis accounts for 20% of these tumors ; the lesions are typically larger than isolated angiomyolipomas, and they are often bilateral and multiple. Angiomyolipomas occur in 80% patients with tuberous sclerosis.The male-to-female sex distributions of angiomyolipoma in patients with tuberous sclerosis are nearly equal, but women outnumber men in terms of prevalence. Angiomyolipomas also occur in young women with lymphangiomyomatosis without other stigmata of tuberous sclerosis. Angiomyolipomas and lymphangiomyomatosis are sometimes considered the forme fruste of tuberous sclerosis. Although an angiomyolipoma is considered benign, rare cases, possibly related to multicentric disease, have been reported regarding extension into the renal vein and/or inferior vena cava (IVC), as well as deposits in the regional lymph nodes.

Most small angiomyolipoma lesions are asymptomatic and found incidentally on imaging studies. As many as 40% are symptomatic; these can cause a palpable abdominal mass, hematuria, or flank pain. The solitary sporadic tumors may cause an acute abdomen and shock as a result of spontaneous hemorrhage in the tumor. The demonstration of fatty attenuation in renal tumor on computed tomography (CT) scanning studies is virtually diagnostic of angiomyolipomas