A comprehensive approach to the CT detection and evaluation of large adrenal masses (≥ 4 cm) part 1: benign adrenal lesions.

With the growing use of computed tomography (CT) scans, there has been a corresponding increase in detection of incidental adrenal lesions. For decades, tumor size has been associated with malignancy, however emerging research has suggested that the majority of large (> 4 cm) adrenal lesions are benign and do not require surgical resection. With CT being the gold-standard imaging modality for evaluating adrenal lesions, it is important to differentiate benign and malignant lesions on imaging to guide clinical management and avoid overtreatment. In this first part of the pictorial essay, we discuss the CT appearances of benign adrenal lesions including adenoma, cyst, myelolipoma, lymphangioma, and neurogenic tumors, to effectively differentiate them from malignant lesions. Malignant adrenal tumors, as well as pheochromocytoma, which is commonly benign but can rarely be malignant, are discussed in detail in part 2 of the paper.