The computed tomography adrenal wash-out analysis properly classifies cortisol secreting adrenocortical adenomas.

Purpose: Adrenocortical lesions are characterized through imaging, hormonal and histopathological analysis. Our aim was to compare the radiological features of adrenocortical lesions with their cortisol-secreting status and histopathological Weiss score.
Methods: Seventy five patients operated between 2004 and 2016 in the University Hospital of Nancy for either adrenocortical carcinomas (ACC) or adrenocortical adenomas (ACA) were enrolled in this study. We collected cortisol parameters, Computed Tomography (CT) scans (unenhanced density, wash-out (WO) analysis) and ¹⁸ F-Fluorodeoxyglucose positron emission tomography/computed tomography ( ¹⁸ F-FDG PET/CT) datas. The histopathological Weiss score ultimately differentiates ACA (score ≤ 2) from ACC (score ≥ 3). One-way ANOVA, Fisher's exact and unpaired t tests were used for statistical analysis with significancy reached at p < 0.05.
Results: There were 23 ACC and 52 ACA with 40 patients (53%) who had an autonomous secretion of cortisol. On CT scan, ACC were larger compared to ACA (108 vs. 37 mm, p < 0.0001). A roughly similar proportion of cortisol-secreting (22/25) and non-secreting (15/19) ACA were atypical (i.e., unenhanced density value ≥ 10 Hounsfield Units [HU]), however 85% of cortisol-secreting vs. 40% of non-secreting ACA were classified as benigns by the relative WO analysis (p = 0.08). Likewise, there was a trend for a higher ¹⁸ F-FDG uptake in cortisol-secreting ACA compared to non-secreting ACA (p = 0.053).
Conclusions: The relative adrenal WO analysis consolidates the benign nature of an ACA, especially in case of cortisol oversecretion, a condition known to compromise the diagnostic accuracy of the 10 HU unenhanced CT attenuation threshold.