title: The "ring sign" of necrotic pheochromocytoma.
abstract: Pheochromocytomas are usually hypervascular tumors exhibiting dense stain during angiography. The cystic nature of the neoplasm or tumor necrosis can result in failure of opacification of the mass or a central lucent area. Four cases of pheochromocytoma are described where a central avascular zone was surrounded by a dense rim of contrast, giving a "ring sign." Since this appearance is best seen in the capillary and venous phases, delayed films are essential.
mesh_terms: D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology; D002648:Child; D006801:Humans; D008875:Middle Aged; D009336:Necrosis; D010673:Pheochromocytoma / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology; D011859:Radiography