cromaffini

Cromaffini, or chromaffin cells, are neuroendocrine cells derived from the neural crest and named for their ability to stain brown with chromium salts in histological preparations, a reaction known as the chromaffin reaction. They are most numerous in the adrenal medulla, where they form a prominent part of the adrenal medullary tissue, but a broader network of chromaffin tissue exists outside the adrenal gland (paraganglia) along the great vessels and in discreet sites such as the organ of Zuckerkandl and the carotid body.

Functionally, chromaffin cells synthesize and secrete catecholamines, predominantly adrenaline (epinephrine) and noradrenaline (norepinephrine), with smaller amounts of dopamine. Secretion is triggered by activation of the sympathetic nervous system: preganglionic sympathetic fibers release acetylcholine, stimulating exocytosis of dense-core granules. The released catecholamines prepare the body for acute stress by increasing heart rate and contractility, dilating airways, promoting glycogenolysis and lipolysis, and modulating blood flow.

Histology and markers: chromaffin cells are typically arranged in nests or sheets and contain dense-core granules visible under electron microscopy. Immunohistochemistry commonly shows positivity for chromogranin A and synaptophysin. In adrenal tissue, chromaffin cells are often intermingled with sustentacular cells that are S-100 positive.

Clinical relevance: tumors arising from chromaffin tissue, such as pheochromocytomas (adrenal) and paragangliomas (extra-adrenal), can secrete catecholamines, causing hypertension, headaches, and tachycardia. Diagnosis relies on measurements of plasma free metanephrines or urinary metanephrines; treatment typically involves alpha-adrenergic blockade followed by surgical removal.