Diagnostic Efficacy of ACR-TIRADS and Nodule Size in Bethesda Category III and IV Thyroid Nodules: a 13-Year Retrospective Analysis

The management of thyroid nodules with indeterminate cytology remains a significant clinical challenge. This study aims to evaluate the malignancy rates of Bethesda III and IV nodules and to investigate the diagnostic efficacy of ACR-TIRADS scoring and nodule size in predicting postoperative histopathological outcomes. A retrospective analysis was conducted on 216 patients who underwent thyroidectomy for Bethesda III and IV nodules at Tekirdağ Namık Kemal University, Department of General Surgery, between 2010 and 2023. Preoperative sonographic descriptors, cytopathological findings, and definitive histopathological results were compared. Statistical analysis included Mann-Whitney U, Chi-square tests, multivariable logistic regression for overall and subgroup cohorts, and Receiver Operating Characteristic (ROC) curve analysis. The study cohort comprised 173 (80.1%) females and 43 (19.9%) males, with a mean age of 52.6 ± 11.8 years. Bethesda III and IV categories accounted for 62.5% and 37.5% of the cases, respectively. The overall malignancy rate was 33.8% (30.3% for Bethesda III and 39.5% for Bethesda IV). Overall, conventional clinical and ultrasonographic parameters exhibited poor discriminatory ability within this surgically treated cohort. However, subgroup multivariable analyses revealed divergent predictive patterns: the analysis demonstrated improved, albeit moderate, discrimination for the Bethesda IV subgroup (AUC: 0.695, Nagelkerke R²: 0.146) compared to the Bethesda III subgroup (AUC: 0.579, Nagelkerke R²: 0.020). Within this surgically treated cohort, indeterminate nodules harbor a substantial malignancy risk approaching 40%. The discriminatory performance of ACR-TIRADS is limited in these resected Bethesda III and IV nodules. Although insufficient to independently avert surgery, ultrasound risk stratification remains a valuable component of multidisciplinary assessment. Molecular diagnostics may help reduce avoidable operations. When inaccessible, shared decision-making should guide the choice between diagnostic surgery and active surveillance.