Incidental adrenal masses are common, with most representing benign, nonfunctional cortical adenomas. The diagnostic approach should consist of a biochemical evaluation for hormonal hypersecretion, as well as an assessment of the risk of malignancy (primary adrenal cancer vs metastasis from another site). The size and appearance of the adrenal tumor on imaging studies are critical to management decisions. Computed tomography (CT) or T1 weighted chemical shift magnetic resonance imaging (MRI) can usually diagnose a cortical adenoma based on characteristics related to intracellular lipid content. However, 30% of cortical adenomas are lipid-poor, and will be classified as indeterminate on CT or MRI. Fluorodeoxyglucose-positron emission tomography (FDG-PET) is a useful method of further characterizing an indeterminate adrenal mass, particularly in an oncology patient in whom identification of an adrenal metastasis will affect disease stage and therapy. FDG-PET has been found to have a sensitivity of 93 to 100% and a specificity of 70 to 100% for the identification of an adrenal malignancy in both oncology and non-oncology patient populations. Indications for adrenalectomy include all functional adrenal tumors, known or suspected primary adrenal cancers that appear resectable, adrenal tumors > 4 cm, and isolated adrenal metastases.
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