pheochromocytoma phe·o·chro·mo·cy·to·ma (fē'ō-krō'mō-sī-tō'mə)
n. pl. phe·o·chro·mo·cy·to·mas or phe·o·chro·mo·cy·to·ma·ta (-mə-tə)
A usually benign tumor of the adrenal medulla or the sympathetic nervous system in which the affected cells secrete increased amounts of epinephrine or norepinephrine.
tumour, most often nonmalignant, that causes abnormally high blood pressure because of hypersecretion of the hormones epinephrine and norepinephrine. Usually the tumour is in the medullary cells of the adrenal gland but may occur elsewhere; e.g., in the chromaffin tissues of the ganglia of the nervous system.
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