A nomogram for preoperative risk evaluation of Bethesda III thyroid nodules.

Background

Bethesda Category III thyroid nodules (AUS/FLUS) pose a diagnostic challenge due to their malignancy rate of 15-30%. This study aimed to develop and validate a preoperative nomogram combining ultrasonographic features and BRAF V600E mutation status to enhance individualized risk assessment.

Methods

We analyzed 173 surgically resected Bethesda III nodules (50 benign, 123 malignant) from a tertiary referral center (2020-2025). Standardized ultrasound characteristics and BRAFV600E status were evaluated. Multivariable logistic regression identified malignancy predictors. Diagnostic performance was assessed using ROC analysis with DeLong's test.

Results

Malignant nodules were significantly smaller than benign ones (8.0 ± 6.0 vs 21.0 ± 13.2 mm, P < 0.001), with higher rates of hypoechogenicity (84.6% vs 50.0%), taller-than-wide shape (47.2% vs 12.0%), and punctate echogenic foci (30.1% vs 12.0%). BRAFV600E positivity occurred in 72.4% of malignancies and correlated with hypoechogenicity (P < 0.001) and taller-than-wide morphology. Multivariable analysis identified four independent predictors: BRAFV600E (aOR 8.56, 95% CI 3.92-18.71), TI-RADS 5 (aOR 4.23, 2.15-8.32), taller-than-wide shape (aOR 6.75, 2.57-17.72), and size ≤ 15 mm (aOR 3.94, 1.92-8.08). The nomogram achieved superior performance (AUC 0.95 vs 0.71 ultrasound alone, ΔAUC + 0.24, P < 0.001) with excellent calibration.

Conclusions

This nomogram combines BRAFV600E status with key ultrasound features to refine preoperative malignancy risk prediction for Bethesda III nodules.