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.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging