Adrenal imaging features and associated pathologic diagnoses: A contemporary, longitudinal analysis

Area of Science:

• Radiology
• Oncology
• Endocrinology

Background:

• Preoperative risk assessment of adrenal nodules relies on imaging features, but evidence quality is often low.
• Current recommendations for adrenal nodule characterization require evaluation.

Purpose of the Study:

• To evaluate the performance of cross-sectional imaging features in predicting adrenal pathology.
• To determine the accuracy of specific imaging characteristics in differentiating benign from malignant adrenal lesions.

Main Methods:

• Retrospective review of adult adrenalectomy cases (2015-2023) with preoperative cross-sectional imaging.
• Exclusion of pheochromocytomas and incidental adrenalectomies.
• Analysis of imaging features including size, Hounsfield units on unenhanced CT, contrast washout on contrast-enhanced CT, and MRI signal characteristics.

Main Results:

• Malignant lesions were significantly larger (6.8 cm vs 4.4 cm) and denser than benign lesions.
• A density threshold of ≤20 Hounsfield units on unenhanced CT reliably excluded malignancy.
• Small malignant lesions (<4.0 cm) were identified in 13.6% of adrenocortical carcinomas and 63.3% of other malignant lesions.
• The density threshold of ≤20 Hounsfield units achieved 65% accuracy in identifying adrenal pathology, correctly classifying 48% of benign lesions.

Conclusions:

• Adrenal lesion size >4.0 cm alone has low specificity for malignancy.
• Absolute contrast washout on CT may miss metastatic lesions.
• A density threshold of ≤20 Hounsfield units on unenhanced CT is a reliable method to exclude adrenal malignancies, potentially preventing unnecessary surgeries.