Walsh & Hoyt: Pheochromocytoma

The adrenal gland consists of two main portions: the cortex and the medulla. The cortex can be further divided into three zones. Outermost is the zona glomerulosa, where aldosterone is produced. This zone is normally under the control of the renin-angiotensin system. Adjacent and internal to the zona glomerulosa is the zona fasciculata, where glucocorticoids and adrenal androgens are produced. Adrenal androgens also are synthesized in the innermost zone of the adrenal cortex, the zona reticularis. The center of the adrenal gland is the adrenal medulla. The adrenal medulla is derived from primitive cells of the neural crest that eventually differentiate into pheochromocytes. These cells produce the catecholamines epinephrine (adrenaline) and norepinephrine (noradrenaline) in a ratio of about 9:1. Within the pheochromocytes, both epinephrine and norepinephrine are bound to adenosine triphosphate and are located in granules that stain darkly when the tissue is fixed with chromic acid. Chromic acid oxidizes catecholamines and indole amines (e.g., serotonin) to brown polymers and the chromium salt is incorporated into the complex. This dusky staining accounts for the name pheochromocytoma (from the Greek phaios [dusky], chroma [color], and kytos [cell]). Stilling introduced the term ""chromophile"" for cells that reacted positively to chromate, and Kohn used the term ""chromaffin"" to describe the reaction itself.