chromaffin

Chromaffin refers to a type of neuroendocrine cell found predominantly in the adrenal medulla and in some paraganglia that stain brown when treated with chromium salts. The term derives from the characteristic chromaffin reaction, a histochemical staining process in which catecholamines and related compounds are oxidized and imbued with a brown to black color.

Chromaffin cells, also called pheochromocytes, originate from neural crest cells and form clusters around extensive capillary networks in the adrenal medulla and in extra-adrenal paraganglia. They synthesize and store catecholamines—primarily epinephrine (adrenaline) and norepinephrine (noradrenaline)—that are released into the bloodstream in response to sympathetic stimulation. Preganglionic sympathetic fibers, via acetylcholine, trigger calcium-dependent exocytosis of these granules.

In function, the catecholamines secreted by chromaffin cells mediate rapid stress responses, influencing heart rate, vascular tone, blood pressure, and metabolic processes such as glucose mobilization.

Histologically, chromaffin cells contain dense-core secretory granules that confer the tissue’s characteristic brown staining with chromaffin reagents. The surrounding tissue includes supportive stroma and a dense capillary network.

Clinically, chromaffin tissue can give rise to tumors such as pheochromocytomas (adrenal) and paragangliomas (extra-adrenal). These tumors may overproduce catecholamines, leading to hypertension, headaches, palpitations, and diaphoresis, and typically require biochemical testing and imaging for diagnosis.