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

Abstract

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!0.0001). In ACCs, the median unenhanced HU value was 34 (range 14-74) in comparison with 5 (K13 to 40) in BATs (P!0.0001). ROC analysis revealed a HU of 21 as threshold with the best diagnostic accuracy (sensitivity 96%, specificity 80%, and AUC 0.89). However, two ACCs that were 5 and 6 cm in size would have been missed. Setting the threshold to 13.9 allowed for 100% sensitivity, but a lower specificity of 68%. Conclusions: This first large study on ACCs confirmed that the vast majority of ACCs have unenhanced HU O21. However, to avoid misdiagnosing an ACC as benign, a threshold of 13 should be used.

Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors

“…• Included: We identified 37 studies for inclusion in the systematic review (49,52,61,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112), with only 18 of them fulfilling the criteria for inclusion in the actual meta-analysis (61,79,80,81,82,83,84,85,86,87,88,89,90,91...…”

Future directions in the diagnosis and medical treatment of adrenocortical carcinoma

“…Size is thought to be the most important predictor for malignancy, with an increase from 52 to 80% specificity for malignancy for tumors larger than 4-6 cm respectively (Sturgeon et al 2006). In the largest series on adrenal imaging so far, Petersenn et al (2015) suggest that a threshold of 13 HU instead of 10 HU should be used to more adequately diagnose ACC. If the characteristics on unenhanced CT followed by contrast-enhanced examinations do not show a classic ACC appearance, MRI can provide additional information regarding the diagnosis (Ilias et al 2007).…”

“…Although these findings together will not always indicate a clear diagnosis, the previously mentioned characteristics on a CT scan are currently used to guide the decision on adrenalectomy. Adrenalectomy is generally performed in case of lesions larger than 4 cm (Petersenn et al 2015).…”

Management of adrenocortical carcinoma: a consensus statement of the Italian Society of Endocrinology (SIE)

“…In addition, differences in single-detector and multi-detector CT helical scanners can generate slightly different attenuation values that could produce different categorization [29]. A recent analysis of the German ACC registry on the largest number of adrenocortical cancers ever evaluated in any adrenal imaging report suggests that 13 HU is the most sensitive threshold to distinguish adenoma from carcinoma; although HU values below 21 most probably indicate a benign lesion, adrenal masses with HU values between 13 and 40 should be considered indeterminate requiring further evaluation [30].…”