Computed tomography criteria for discrimination of adrenal adenomas and adrenocortical carcinomas: analysis of the German ACC registry

Objective Thresholds of 2-20 hounsfield units (HU) in unenhanced computed tomography (CT) are suggested to discriminate benign adrenal tumors (BATs) from malignant adrenal tumors. However, these studies included only low numbers of adrenocortical carcinomas (ACCs). This study defines a HU threshold by inclusion of a large cohort of ACCs. Design Retrospective, blinded, comparative analysis of CT scans from 51 patients with ACCs (30 females, median age 49 years) and 25 patients with BATs (12 females, median age 64 years) diagnosed during the period of 2005-2010 was performed. Methods Tumor density was evaluated in unenhanced CT by two blinded investigators. Results Median tumor size was 9 cm (range 2.0-20) for ACCs vs 4 cm (2.0-7.5) for BATs (P Conclusions This first large study on ACCs confirmed that the vast majority of ACCs have unenhanced HU >21. However, to avoid misdiagnosing an ACC as benign, a threshold of 13 should be used.