EP63 - ECE_3317 - Natural history of large adrenal tumors

Abstract

The aim of this study was to characterize large adrenal tumors (LATs), assess the accuracy of imaging diagnostics in detecting malignant LATs, and determine whether further follow-up of seemingly benign LATs is necessary. We investigated the clinical, biochemical, and imaging characteristics at presentation and follow-up in a retrospective single-center cohort of patients with adrenal tumors ≥4 cm in diameter during the period from June 2013 to June 2023. Of 1473 patients with adrenal tumors, 269 (18.3%) had adrenal masses measuring ≥4 cm in diameter, 220 patients were included in the study. Among LATs 34.6% were adrenocortical adenomas, 27.3% other benign adrenal tumors, 17.3% adrenocortical carcinomas, 11.4% other malignant tumors, 9.6% pheochromocytomas. 44.7% of tumors were non-functioning and 37.8% were producing corticosteroids. Sensitivity of an unenhanced computed tomography attenuation in detecting malignancy was 100% using the threshold >10 Hounsfield Units and 89.5% for >20 Hounsfield Units (with specificity 66.1% and 81.4% respectively). Magnetic resonance with chemical shift analysis also had high sensitivity (94.4%), but low specificity (56.8%). 18F-fluorodeoxyglucose-positron emission tomography integrated with computed tomography had 100% sensitivity using adrenal liver ratio >1, when the maximum standardized uptake value >5 cutoff was employed, sensitivity remained high (100%) while specificity improved (82.1% vs 100%). 87 tumors remained under follow-up. The mean follow-up was 30.1 months. Significant tumor growth was observed in 4 cases (4.6%). 3 of these tumors were myelolipomas, 1 was indeterminate mass in a patient with extraadrenal malignancy. Adrenalectomy was performed in 6 patients (6.9%). While they were initially assessed as adrenocortical adenomas, in 5 of them histopathology revealed benign lesions and in one an adrenocortical carcinoma. The risk of developing mild autonomous cortisol secretion among non-functioning lesions was 6.7%. No progression to overt Cushing's syndrome was observed. While the risk of malignancy increases with tumor size, most large adrenal tumors are benign. Imaging sensitivity for detecting malignancy is high in LATs. No malignancy was diagnosed in lesions with certain benign features (homogenous <10 HU). LATs that do not meet these criteria should be assessed by a multidisciplinary team and be subjected to continued follow-up.