The Diagnostic Value of ACR TI-RADS Descriptive Terminology for TR4-5 Nodules Stratified by Diameter.

To evaluate the diagnostic accuracy of ACR TI-RADS descriptors for TR4-5 thyroid nodules across different diameters. This retrospective study analyzed 772 pathologically confirmed TR4-5 nodules categorized into ≤ 1 cm (n = 505) and > 1 cm (n = 267) groups. Diagnostic concordance (Kappa test), risk factors (logistic regression), and discriminatory performance (AUC) of ultrasound features were compared. Interobserver agreement was significantly higher in the > 1 cm group (Kappa = 0.432 ± 0.048 vs. 0.225 ± 0.076, p < 0.05). For ≤ 1 cm nodules, irregular margins (OR = 3.22), taller-than-wide shape (OR = 2.58), and punctate echogenic foci (OR = 2.35) were key predictors; for > 1 cm nodules, extrathyroidal extension (OR = 11.13), irregular margins (OR = 10.12), and solid composition (OR = 5.28) demonstrated stronger associations. Margin characteristics achieved the highest diagnostic accuracy in both groups (AUC: 0.642 vs. 0.734). ACR TI-RADS exhibits diameter-dependent diagnostic performance, with margin analysis remaining the most reliable feature across sizes. These findings underscore the need for diameter-specific risk stratification in thyroid nodule management.