Adrenal 'nonadenoma' — clinical characteristics and risk of malignancy

Introduction: There is an increasing number of adrenal tumours discovered incidentally during imaging examinations performed for many different indications. Based on imaging results, it is possible to differentiate benign from malignant adrenal masses, although there is still a number of equivocal imaging findings. Our study presents 77 cases of adrenal tumours in which imaging was inconclusive and the final diagnosis was stated only after surgery and histopathological examination. Material and methods: Retrospective data analysis: 77 cases of indeterminate adrenal tumours with a presumptive diagnosis of “nonadenoma” in patients operated within a 16-year period (2004–2019). None of the patients had a history of malignancy, and all tumours were hormonally inactive. On contrast-enhanced computed tomography (CT), the native density of all tumours was higher than 10 Hounsfield Units (HU), and the absolute percentage washout (APW) and relative percentage washout (RPW) were lower than 60% and 40%, respectively. Results: The most common findings were adrenal adenoma (25.9%), macronodular adrenal hyperplasia (16.9%), ganglioneuroma (15.6%), and haemorrhage with posthaemorrhagic changes (13%). In total, there were 12 various histopathological diagnoses in this group. There were only 2 (2.6%) malignant (adrenal cancer and leiomyosarcoma) and 3 (3.9%) potentially malignant (pheochromocytoma) lesions in this group. Conclusions: It is often impossible to make a correct diagnosis in a clinical setting until it is histologically verified. “Nonadenoma” adrenal tumours constitute a heterogeneous group including very rare pathologies. The risk of malignancy in indeterminate adrenal tumours is relatively low.