What is the first-line imaging modality and suspicious features for evaluating an adrenal incidentaloma?

• A. Ultrasound; suspicious features include homogeneous enhancement.
• B. CT or MRI; suspicious features include size >4 cm, irregular margins, heterogeneous enhancement, or invasion of adjacent structures.
• C. PET scan only.
• D. X-ray; suspicious features include calcifications.

Answer: (B)

Evaluating an adrenal incidentaloma relies on cross-sectional imaging to characterize the lesion. CT with an adrenal protocol is usually the first choice, and MRI is a strong alternative when CT isn’t suitable or more detail is needed. Ultrasound isn’t ideal for reliably assessing adrenal lesions, and PET is not a first-line tool for initial evaluation.

The imaging features that raise concern for malignancy include a lesion size greater than 4 cm, irregular margins, heterogeneous enhancement, and invasion of adjacent structures. These findings suggest a higher risk of a malignant process, such as adrenocortical carcinoma, and push toward further workup or surgical consideration. By contrast, smaller lesions with smooth, homogeneous appearance—especially if CT shows lipid-rich, low attenuation—are more likely benign adenomas.