Background: Adrenal masses are discovered in 5% of cross-sectional abdominal imaging scans. Work-up aims at exclusion of malignancy and hormone excess. However, estimates of these risks presently derive from retrospective studies only, mostly small and with significant selection bias.
Methods: Prospective multi-centre study (20112016) in 21 centres (17 countries) of the European Network for the Study of Adrenal Tumours (ENSAT) with consecutive enrolment of patients with newly diagnosed adrenal mass. Extra-adrenal malignancy and biochemically proven phaeochromocytoma were exclusion criteria. Diagnosis was confirmed by histology or imaging follow-up.
Results: We enrolled 2190 patients with an adrenal mass (median size 3 cm). Overall, 1933 (88%) had an adrenocortical adenoma (ACA) and 73 (3%) were diagnosed with other benign masses (adrenomyelolipoma, ganglioneuroma, schwannoma, cyst). In addition, 155 patients (7.1%) were diagnosed with adrenocortical carcinoma (ACC) and 29 (1.3%) with other malignant masses (metastases, primary adrenal lymphoma, sarcoma). Risk of ACC was highest in young patients (<40 yrs 22%; 4060 yrs 9%; >60 yrs 5%). In adrenal masses <4 cm diameter, ACC was diagnosed in only 0.2% (3/1666) whereas an incidence of 29% (152/524) was found in masses >4 cm.
CT imaging with quantification of tumour density in Hounsfield units (HU) was available for 1252 ACA patients; of those, only 67% had HU<10 indicative of benign disease (1020 HU 14%; >20HU 19%). Similarly, 24% of 233 ACA patients characterised by MRI showed no drop in signal intensity in chemical shift analysis, wrongly suggestive of malignant disease. Incidence of subclinical Cushing syndrome was 33% (517/1555) in patients with dexamethasone overnight suppression test results. Adrenalectomy was performed in 18.6% (379/2035) of patients with benign tumours.
Conclusion: Risk of ACC needs to be seriously considered in patients with adrenal incidentaloma. On the other hand, benign masses are frequently misclassified as malignant by routine imaging, resulting in a high rate of unnecessary adrenalectomies.
07 Nov 2016 - 09 Nov 2016