Imaging Modalities for Adrenocortical Tumors

Abstract

Incidental adrenal masses are increasingly being detected due to the more frequent use of high-resolution thoraco-abdominal imaging techniques. Almost all adrenal masses can be definitively characterized using imaging and biochemical studies alone. The majority of adrenal cortical tumors are benign. Densitometry using unenhanced computed tomography (UCT) and CT contrast medium washout testing, magnetic resonance imaging (MRI) with chemical shift averaging, and fluorine-18 fluorodeoxyglucose positron emission computed tomography ([FDG] PET/CT) are the principal modalities used to help differentiate a benign from a malignant adrenal mass. In most patients, a single imaging study is sufficient to characterize an adrenal mass and secondary imaging studies are unnecessary. Key elements that help guide management include a prior history of malignancy, the functional status of the mass, and whether the imaging phenotype is suggestive of benign or malignant disease. The imaging phenotype can be distinguished based on the size, morphology, lipid content, intravenous washout characteristics, and metabolic activity of the adrenal mass. When the imaging phenotype and the clinical and biochemical evaluation are consistent with a nonfunctioning adenoma, follow-up imaging is recommended in 3–6 months and then annually for 1–2 years, with repeat hormonal evaluation on an annual basis for 5 years.