Adrenal masses are common findings on abdominal CT or MRI scans (1-7% prevalence with increasing age). The majority (70-80%) of such “incidentalomas” are clinically nonfunctional, and the probability of an adrenal carcinoma is low (<0.01%). Genetic syndromes such as MEN 1, MEN 2, Carney syndrome, and McCune-Albright syndrome are all associated with adrenal masses. The first step in evaluation is to determine the functional status by measurement of plasma free metanephrines to screen for pheochromocytoma (Fig. 171-2). In a pt with a known extraadrenal malignancy, there is a 30-50% chance that the incidentaloma is a metastasis. Additional hormonal evaluation should include 24-h urine for urinary free cortisol or overnight 1-mg dexamethasone suppression testing, plasma renin activity/aldosterone ratio in hypertensives, DHEAS in women with signs of androgen excess, and estradiol in males with feminization. Fine-needle aspiration is rarely indicated and absolutely contraindicated if a pheochromocytoma is suspected. Adrenocortical cancer is suggested by large size (>4-6 cm), irregular margins, tumor inhomogeneity, soft tissue calcifications, and high unenhanced CT attenuation values (>10 HU).