pheochromocytoma is a neoplasm composed of cells similar to the chromaffin cells of the mature adrenal medulla. pheochromocytomas occur in patients of all ages, and may be sporadic, or associated with a hereditary cancer syndrome, such as multiple endocrine neoplasia (men) types iia and iib, neurofibromatosis type i, or von hippel-lindau syndrome. only 10% of adrenal pheochromocytomas are malignant, while the rest are benign tumors. the most clinically important feature of pheochromocytomas is their tendency to produce large amounts of the catecholamine hormones epinephrine (adrenaline) and norepinephrine. this may lead to potentially life-threatening high blood pressure, or cardiac arrythmias, and numerous symptoms such as headache, palpitations, anxiety attacks, sweating, weight loss, and tremor. diagnosis is most easily confirmed through urinary measurement of catecholamine metabolites such as vma and metanephrines. most pheochromocytomas are initially treated with anti-adrenergic drugs to protect against catecholamine overload, with surgery employed to remove the tumor once the patient is medically stable.