adrenal lesions are under-reported in clinical practice. Prevalence figures for adrenal incidentalomas should therefore be interpreted with caution, especially in multi-center settings.

In this prospective cohort study 6·6 per cent of patients with an AI had surgery and benign hormone-producing tumours were verified in 3·1 per cent. Repeat CT and hormone evaluation after 2 years did not increase the sensitivity for diagnosis of malignant or hormone-producing tumours.

An adrenal lesion occurring in a patient with past malignancy has a high likelihood of representing a benign lesion, and even in patients with present signs of malignant disease at least one fourth to one half of such lesions are benign. Dedicated adrenal imaging including computed tomography attenuation measurements with wash-out characteristics, in addition to biochemical testing for adrenal dysfunction, is highly recommended in these cases, especially in patients without any other signs of metastatic spread.