How Often Are Adrenal Incidentalomas Malignant?

Nearly all small, incidentally noted adrenal nodules (“incidentalomas”) with radiodensity less than 10 Hounsfield units (HUs) on noncontrast CT scans are benign adenomas. But the 10-HU threshold is not valid on contrast-enhanced scans, where incidentalomas are often discovered. This retrospective study from 12 academic medical centers examined how often such lesions turn out to be malignant.

Researchers identified 1500 adrenal incidentalomas that measured ≥1 cm and were first noted on contrast-enhanced CT in patients with no history of cancer. Criteria to confirm that lesions were benign included subsequent noncontrast CT with nodule density <10 HU, stable size on serial imaging ≥1 year later, or no clinical evidence of adrenal cancer…