the adrenal medulla is located anatomically at the center of each adrenal gland, and is composed of neuroendocrine (chromaffin) cells which produce and release epinephrine (adrenaline) into the bloodstream in response to activation of the sympathetic nervous system. neuroblastoma and pheochromocytoma are the two most important tumors which arise from the adrenal medulla. both tumors may also arise from extra-adrenal sites, specifically, in the paraganglia of the sympathetic chain.