To explore the pathological characteristics of adrenal masses based on various tumor diameter and unenhanced computed tomography(CT) attenuation value, and evaluate the value of the two parameters in the assessment of the benign and malignant nature of adrenal masses.

The data of 1 367 patients who underwent adrenalectomy in Nanjing Drum Tower Hospital from January 2017 to October 2022 were retrospectively collected. The adrenal masses were divided into four groups according to tumor diameter and unenhanced CT attenuation value, and the clinical and histopathological characteristics of the four groups were compared respectively. Logistic regression was used to analyze the correlation between tumor diameter, non-contrast CT attenuation value and malignant adrenal masses, and receiver operating characteristic(ROC) curve was used to assess the diagnostic value of both in benign and malignant adrenal masses.

The proportion of adrenocortical carcinoma and other malignant tumors increased with the rise of tumor diameter or unenhanced CT attenuation value. After adjusting for age and gender, tumor diameter(OR=1.624, 95%CI 1.464-1.803, P<0.001) and unenhanced CT attenuation value(OR=1.108, 95%CI 1.079-1.138, P<0.001) were predictors of malignant adrenal masses. The tumor diameter and unenhanced CT attenuation value in diagnosing malignant adrenal masses had area under the ROC curve(AUC) of 0.838 and 0.892, respectively. With the optimal cut-off values of >3.4 cm and >30 HU, the sensitivity was 75.5% and 83.7%, and the specificity was 80.5% and 84.4%, respectively. The combination of tumor diameter >3.4 cm and unenhanced CT attenuation value >20 HU had an AUC of 0.927, with a sensitivity of 71.4% and a specificity of 90.1% in diagnosing malignant adrenal masses.

Tumor diameter and unenhanced CT attenuation value has important significance in the differential diagnosis of benign and malignant adrenal masses. A combination of tumor diameter (>3.4 cm) and unenhanced CT attenuation value (>20 HU) demonstrates best diagnostic efficiency. Clinical application of this combined index can effectively diagnose malignant adrenal masses while avoiding unnecessary investigations or surgery.

Adrenal masses; Adrenal incidentaloma; Tumor diameter; Unenhanced CT attenuation value