What is ANGIOMYOLIPOMA of the kidney?
Angiomyolipomas are benign tumors; the majority are small and single, although they vary in size from a few millimeters to larger than 20 cm. At gross pathologic examination, the tumors are round or lobulated and yellow to gray on cut sections because of their fat content. Angiomyolipomas are composed of fat, vascular, and smooth muscle elements; however, angiomyolipomas are not hamartomas, because fat and smooth muscle are not normal constituents of the renal parenchyma. Rather, an angiomyolipoma is a choristoma; that is, as the name implies, it is composed of variable amounts of vascular, muscular, and fatty tissues. In 5% of the tumors, fatty elements may be detected only at microscopy7 ; this limitation makes accurate characterization on the basis of radiologic findings alone impossible. The blood vessels in angiomyolipomas frequently have an angiomatous arrangement, wherein the vessels are tortuous and thick walled. The blood vessels do not have elastic tissue, but they do have a