Adrenal incidentaloma -: experience of a standardized diagnostic programme in the Swedish prospective study

Objective. To report the 5-year experience of a diagnostic programme for adrenal incidentaloma with special emphasis to diagnose hormonally active and malignant lesions. Design. A prospective study in which new cases of adrenal incidentalomas in Sweden have been evaluated by a standardized diagnostic protocol between January 1996 and July 2001. Setting. Thirty-three different Swedish hospitals have contributed with cases. Subjects. A total of 381 patients (217 females, 164 males) with adrenal incidentalomas were studied. Interventions. Diagnostic procedures were undertaken according to a standardized programme. Operation was recommended if the incidentaloma had a size of more than 3-4 cm or if there was a suspicion of a hypersecreting tumour. Main outcome measures. The size of the incidentaloma, clinical characteristics of the patients and results of biochemical diagnostic tests were registered. Results. The median age of the patients was 64 years (18-84 years), and the median size of the incidentalomas was 3 cm (1-20 cm). A total of 85 (22%) patients were operated. Twenty of these patients were diagnosed with a benign hypersecreting tumour and 14 with a malignant tumour. Fourteen of 15 operated patients with diagnosed pheochromocytoma had elevated 24-h urinary noradrenaline and all of the patients operated because of a biochemical suspicion of aldosterone or cortisol hypersecretion (n = 6) were found to have adrenal adenomas. Of the 14 operated patients with malignant diseases, 10 were adrenal carcinomas (median size 10 cm; range 4-16 cm). In a multiple logistic regression model, incidentaloma size was significantly associated with the risk of a malignant tumour (P = 0.009), and there was a tendency of an association between age/male sex and the risk of a malignancy (both, P = 0.07). Conclusion. In this Swedish multicentre study of 381 cases with adrenal incidentalomas, 5%, had benign hypersecreting tumours and nearly 40% had malignant tumours. The results of the biochemical diagnostic tests used had a high compatibility with the histological diagnosis found at operation in the patients with hypersecreting tumours. Tumour size, male gender and high age were predictive for the risk of a malignant tumour. A follow-up of the patients is warranted in order to establish whether there are undiscovered cases of malignant or hypersecreting tumours amongst the nonoperated patients.