The Landmark Series: Evaluation and Management of Adrenal Incidentalomas

Adrenal incidentalomas are adrenal masses ≥ 1 cm discovered on imaging studies for unrelated clinical conditions. The prevalence of adrenal incidentalomas has increased as a byproduct of the widespread use of cross-sectional imaging, particularly in older adults. The clinical significance of adrenal incidentalomas varies based on tumor size, hormonal activity, and imaging characteristics. While most adrenal incidentalomas are benign and asymptomatic, a significant minority are hormonally active or malignant, necessitating careful evaluation and management. Adrenal hormone secretion can have significant clinical implications. Biochemical testing is crucial to assess for hormone excess, including steroid hormones (mineralocorticoids, glucocorticoids, and androgens), which are made in the adrenal cortex, as well as catecholamines, which are made in the adrenal medulla. Non-contrast computed tomography (CT) is the preferred modality for evaluating adrenal nodules as it allows for assessment of tissue density in Hounsfield units (HU). Benign lesions typically have an homogeneous appearance with HU ≤ 10. Contrast-enhanced CT with delayed washout can help differentiate benign tumors from malignant tumors. Tumors ≥ 4 cm, or those with indeterminate features may require further imaging, such as magnetic resonance imaging (MRI) or positron emission tomography (PET)/CT. The management of adrenal incidentalomas is determined by hormonal secretion and imaging characteristics. Surgical resection is recommended for functional tumors and those that are suspicious for malignancy, including tumors ≥ 4 cm in size and those with rapid growth. Non-functional tumors < 4 cm may undergo imaging surveillance. The goal of this review is to summarize the contemporary literature and guidelines on adrenal incidentalomas, and to describe the key principles regarding evaluation and management.