RESUMEN
BACKGROUND: This prospective cohort study investigated the incidence, clinical features and natural history of incidentally discovered adrenal mass lesions (adrenal incidentaloma, AI) in an unselected population undergoing radiological examination. METHODS: During an 18-month period, all patients with AI were reported prospectively from all 19 radiology departments in western Sweden. Inclusion criteria were: incidentally discovered adrenal enlargement or mass lesion in patients without extra-adrenal malignancy on detection. Clinical and biochemical evaluation was performed on inclusion and after 24 months. Computed tomography (CT) of the adrenals was scheduled at 4, 12 and 24 months. Magnetic resonance imaging was performed for lesions larger than 20 mm. The indications for surgical excision were: hormone activity, lesion diameter more than 30 mm, lesion growth or other radiological features suspicious of malignancy. RESULTS: Of 534 patients assessed for eligibility, 226 (mean age 67 years, 62·4 per cent women; mean lesion diameter 23·9 mm, 22·6 per cent bilateral) fulfilled the inclusion criteria. Mean follow-up was 19·0 months. After baseline evaluation, 14 patients had surgery owing to primary hyperaldosteronism (3), catecholamine-producing tumour (1), tumour size (6), size and indication of subclinical hypercortisolism (3) and metastasis (1). No hypersecreting lesions were confirmed during follow-up; one patient underwent adrenalectomy for a suspected phaeochromocytoma (adrenocortical adenoma at histopathology). No primary adrenal malignancy was found. CONCLUSION: 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.