Pheochromocytoma

Pheochromocytomas are catecholamine-secreting tumors typically arising in about 90% of cases from adrenomedullary tissue and in about 10% of cases from extraadrenal chromaffin tissue. Those arising from extraadrenal tissue are commonly known as paragangliomas or chemodectomas, but all pheochromocytomas display similar histo­pathological characteristics. Paragangliomas arise mainly from chromaffin tissue adja­cent to sympathetic ganglia of the neck, mediastinum, abdomen, and pelvis. Others may arise from a collection of chromaffin tissue around the origin of the inferior mesenteric artery, the organs of Zuckerkandl. Most represent sporadic tumors and only about 10% of pheochromocytomas are familial. In contrast to sporadic pheochromocyto­mas that are usually unicentric and unilateral, familial pheochromocytomas are often multicentric and bilateral (1). Pheochromocytomas are rare endocrine tumors, which, according to different reviews and statistics account for approx 0.05% to 0.1% of patients with any degree of sustained hypertension (2). However, this probably accounts for only 50% of persons harboring a pheochromocytoma, when it is considered that about half the patients with pheochromocytomas have only paroxysmal hypertension or are normotensive. Also, despite the low incidence of pheochromocytoma in patients with sustained hypertension, it must also be considered that the prevalence of sustained hypertension in the adult population of Western countries is between 15 and 20% (3,4).