Diagnostic Performance of European and American College of Radiology Thyroid Imaging Reporting and Data System Classification Systems in Thyroid Nodules Over 20 mm in Diameter

Objective: The challenge of selecting thyroid nodules for fine needle aspiration (FNA) cytology has led to the development of the Thyroid Imaging Reporting and Data System, primarily in 2 formats: European Thyroid Imaging Reporting and Data System (EU-TIRADS) and American College of Radiology Thyroid Imaging Reporting and Data System (ACR-TIRADS). Clinical observations suggest imperfect risk assessment for TIRADS 3 nodules >= 20 mm. This study aimed to evaluate the efficacy of TIRADS systems in distinguishing benign from malignant nodules in this subgroup. Methods: From May 2023 to March 2024, 1094 patients with thyroid nodules were referred for ultrasound at a University Hospital. Data on clinical, ultrasound, cytological, and histopathological parameters were collected. Nodules >= 20 mm were categorized by EU-TIRADS and ACR-TIRADS, and their predictive performance for malignancy was assessed through postthyroidectomy histopathology or FNA cytology (Bethesda classification). Results: Two hundred sixty-seven patients (mean age 60.3 +/- 14.3 years; 46 men, 221 women) with 308 nodules were analyzed. Twenty-two malignancies and 286 benign nodules were recorded. Recalculating European Thyroid Imaging Reporting and Data System 3 performance using 25-mm and 30-mm thresholds (ACR-modified EU-TIRADS) avoided 24% and 41% of FNAs, respectively, while ACR-TIRADS would prevent 26.6% (P > .05). Two malignancies were missed. Conclusion: EU-TIRADS and ACR-TIRADS show similar efficacy when using a 25 mm FNA threshold. Raising the cutoff for FNA in European Thyroid Imaging Reporting and Data System 3 nodules could reduce unnecessary procedures but may increase the risk of missed malignancies, impacting patient outcomes.