The 2004 WHO classification of endocrine tumors defines pheochromocytoma as a tumor arising from catecholamine-producing chromaffin cells in the adrenal medulla -- an intra-adrenal paraganglioma.

Serotonin is produced peripherally by the intestinal chromaffin cells and centrally by nuclei found in the lower pons and upper brain stem (Mills, 1997). It regulates emotional, personality ...