CT Morphologic Features and Size Criteria in Differentiating Benign from Malignant Adrenal Tumors

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Background: Differentiating benign from malignant adrenal tumors is critical for determining appropriate clinical management. Although histopathology is the definitive diagnostic tool, contrast-enhanced computed tomography (CT) offers valuable non-invasive insights. Specific morphologic features- such as size, shape, margins, and enhancement patterns- can help predict malignancy. Establishing reliable CT-based criteria enhances diagnostic confidence and aids in selecting patients who may benefit from surgery or further evaluation. Objective: To evaluate the diagnostic value of CT morphologic features and tumor size in distinguishing benign from malignant adrenal tumors. Methods: This cross-sectional study was conducted at the Department of Radiology and Imaging, Bangladesh Medical University (BMU), Dhaka, over a two-year period and included 30 patients with clinically or radiologically suspected adrenal masses. All patients underwent contrast-enhanced CT (CECT) using a standardized adrenal protocol, including unenhanced, portal venous, and delayed phases. Tumor characteristics such as size, shape, margins, enhancement pattern, internal architecture, necrosis, calcification, and attenuation were assessed. CT findings were interpreted by radiologists blinded to histopathological results. Final diagnoses were confirmed by histopathological examination of biopsy or surgical specimens. CT features and lesion size were then correlated with histopathological outcomes to evaluate their significance. Results: Among the 30 patients evaluated, the mean age was 40.9 ± 17.8 years, with a male-to-female ratio of 1.3:1. CT revealed left-sided adrenal masses in 40%, right-sided in 33.3%, and bilateral involvement in 26.7%. Most lesions (63.3%) were <4 cm, and 53.3% appeared hypodense on pre-contrast imaging. Post-contrast, 50% of lesions showed homogeneous enhancement, while 46.7% showed heterogeneous enhancement. Hemorrhage and necrosis were noted in 23.3% of cases, and invasion into adjacent structures was observed in 6.7%, both exclusively in malignant lesions. Hypodensity was predominantly seen in benign lesions (46.6%), whereas hemorrhage, necrosis, and invasion were exclusive to malignancies. Among lesions <4 cm, 94.7% were benign; among those ≥4 cm, 54.5% were malignant. The odds of a lesion ≥4 cm being malignant were 21 times higher (OR: 21; 95% CI: 2.1–223.6; p = 0.002). Malignant tumors had a significantly larger mean diameter (8.05 ± 5.06 cm) than benign tumors (3.90 ± 2.14 cm; p = 0.003). Adrenal adenoma was the most common lesion (50%), followed by hyperplasia (13.3%) and adrenocortical carcinoma (10%). Conclusion: CT morphologic features, particularly lesion size, enhancement pattern, and structural alterations such as necrosis or invasion, are valuable indicators for distinguishing benign from malignant adrenal tumors. Lesions ≥4 cm and those showing heterogeneous enhancement or invasive characteristics were significantly associated with malignancy.

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