Angiomyolipomas are the most common benign tumour of the kidney and are composed of blood vessels, smooth muscle cells and fat cells. Angiomyolipomas are strongly associated with the genetic disease tuberous sclerosis
, in which most individuals will have several angiomyolipomas affecting both kidneys. They are also commonly found in women with the rare lung disease lymphangioleiomyomatosis. Angiomyolipomas are less commonly found in the liver and rarely in other organs. Whether associated with these diseases or sporadic, angiomyolipomas are caused by mutations in either the TSC1 or TSC2 genes, which govern cell growth and proliferation.