SUN-483 - Contrast-Enhanced CT and Clinical Predictors for Differential Diagnosis of Non-Adenomatous Adrenal Masses: A Pathology-Confirmed Cohort Study

Background: Unenhanced CT attenuation is well established for identifying lipid-rich adenoma, however many non-adenomatous adrenal masses show overlapping unenhanced HU, complicating differentiation among clinically high-stakes etiologies. Quantitative evidence comparing contrast-enhanced CT parameters across multiple non-adenomatous pathologies remains limited.

Objective: To quantify the diagnostic value of multiphase contrast-enhanced CT and clinical factors for differentiating six pathology-confirmed non-adenomatous adrenal entities and to develop an integrated model for PPGL prediction.

Methods: We retrospectively analyzed 100 patients with pathologically confirmed non-adenomatous adrenal masses imaged with multiphase contrast-enhanced CT (2018–2024): PPGL (n=49), histoplasmosis (n=20), adrenocortical carcinoma (ACC; n=14), lymphoma (n=7), myelolipoma (n=6), and ganglioneuroma (n=4). Imaging metrics included unenhanced HU, venous HU, delayed HU, absolute enhancement (venous-unenhanced), and lesion size; clinical variables included age, sex, and BMI. Group differences were tested by ANOVA with effect sizes and Bonferroni-adjusted pairwise comparisons. Multivariable logistic regression models were compared for PPGL prediction using DeLong tests.

Results: Absolute enhancement showed strong discrimination (F=8.55, p< 0.0001, η²=0.471). PPGL demonstrated the highest enhancement (61.4±27.6 HU), significantly greater than histoplasmosis (18.6±20.4 HU; p< 0.0001; d=1.77), ACC (31.2±12.5 HU; p=0.026; d=1.41), and myelolipoma (10.0±19.0 HU; p=0.005; d=2.17). Myelolipoma showed characteristic fat attenuation (unenhanced HU −13.0±46.8). ACC had markedly larger lesions (146.0±44.1 mm; p< 0.0001 vs others). For PPGL prediction (n=59), the combined model (age, sex, size, enhancement) achieved AUC 0.926 (95%CI 0.85-1.00), sensitivity 82.6%, specificity 94.4%, outperforming clinical-only (AUC 0.824; p=0.021) and imaging-only models (AUC 0.879; p=0.042).

Conclusion: Integrating contrast-enhanced CT with clinical factors enables accurate classification of non-adenomatous adrenal masses. Enhancement >60 HU provides high specificity for PPGL, while size >100 mm strongly suggests ACC. This pragmatic model uses routinely available parameters and may reduce unnecessary invasive procedures while accelerating appropriate workup and management.

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