Ans. C. Pheochromocytoma. (Ref. Robbin's 8th/pg. 1159)Robbins pathology 8th edition, page no.1159.......# Microscopically, pheochromocytomas are composed of polygonal to spindle-shaped chromaffin cells and their supporting cells, compartmentalized into small nests, or "Zellballen," by a rich vascular network.Histopathologv of Pheochromocytoma:# Microscopically, pheochromocytomas are composed of polygonal to spindle-shaped chromaffin cells and their supporting cells, compartmentalized into small nests, or "Zellballen," by a rich vascular network.# The cytoplasm of the neoplastic cells often has a finely granular appearance, highlighted by a variety of silver stains, because of the presence of granules containing catecholamines.# Electron microscopy reveals variable numbers of membrane-bound, electron-dense granules, representing catecholamines and sometimes other peptides. The nuclei of the neoplastic cells are often quite pleomorphic.# Both capsular and vascular invasion may be encountered in benign lesions, and the presence of mitotic figures per se does not imply malignancy.# Therefore, the definitive diagnosis of malignancy in pheochromocytomas is based exclusively on the presence of metastases. These may involve regional lymph nodes as well as more distant sites, including liver, lung, and bone.