Predictors of malignancy for treatment direction in patients with nonfunctioning adrenal incidentaloma

Adrenal incidentalomas (AI) are predominantly nonfunctional and benign, and their detection and differential diagnosis are aided by computed tomography (CT). A nonfunctioning adrenal incidentaloma (NFAI) usually requires regular follow-up; however, adrenalectomy may be necessary in certain patients. This study aimed to evaluate prognostic predictors to guide the treatment approach for AIs.

This retrospective, single-center study involved patients diagnosed with NFAI from January 2000 to December 2020. Patients were divided into surgery and observation groups. A subgroup analysis compared malignant and benign adenoma within the surgery group.

A total of 307 patients were included, with 127 in the surgery group and 180 in the observation group. The surgery group displayed distinct morphological and malignant potential features in CT scans more frequently than the observational group did. The malignant subgroup exhibited more irregular borders on CT, and a higher number of patients with absolute washout under 60 % and relative washout under 40 % compared with the benign adenoma subgroup. Interestingly, within the surgery group, the mean tumor size was <4 cm for the both malignant and benign adenoma subgroups.

Characterizing NFAI is important for appropriate treatment, as not all AIs have a favorable prognosis. CT findings associated with malignant potential, such as Hounsfield unit and washout values, were useful in determining the need for surgical treatment. However, the conventional criterion of a 4-cm size threshold for surgery was not a reliable malignancy predictor. Surgical resection should be considered for specific patient groups to ensure proper treatment over mere observation.