7. Pheochromocytoma

Pheochromocytoma is a rare tumor of the adrenal medulla composed of chromaffin cells and is a pharmacologically volatile, potentially lethal catecholamine-containing tumor of chromaffin tissue. It is part of the paraganglioma (PGL). These neuroendocrine tumors can be sympathetic, where they release catecholamines into the bloodstream which cause the most common symptoms, including hypertension, tachycardia, sweating, and headaches. Some PGLs may secrete little to no catecholamines, or only secrete paroxysmally (episodically), and other than secretions, PGLs can still become clinically relevant through other secretions or mass effect. PGLs of the head and neck are typically parasympathetic and their sympathetic counterparts are predominantly located in the abdomen and pelvis, particularly concentrated at the organ of Zuckerkandl at the bifurcation of the aorta.