TIRADS (Thyroid Imaging Reporting and Data System) and Bethesda Categorization of Thyroid Nodules: Single Institution Experience
Introduction: Thyroid imaging reporting and data system (TIRADS) and Bethesda categories attribute malignancy risks and propose recommendations, aiming to standardize radiologists’ and pathologists’ interpretation and triage of nodules into surgery or follow-up. We intend to gauge the risk of TIRADS and Bethesda after introducing these techniques to this institution.
Methods: A cross-sectional, descriptive, and analytical study, with retrospective data analysis, was performed. A total of 906 thyroid nodules from 842 consecutive patients, examined between 01/01/2012 and 31/12/2014, were included. Histological confirmation was obtained in 173 nodules (19.1%). Cytology was categorized by the Bethesda system. Ultrasound images of 743 nodules were stratified into TIRADS categories. Malignancy risk was estimated for each TIRADS and Bethesda category.
Results: Nodule malignancy rate was 26.7% in 2012, 36.9% in 2013, and 55.2% in 2014. The number of nodules included in TIRADS strata 2; 3; 4a; 4b, and 5 were 25; 354; 298; 49, and 17 respectively. There was a statistically significant difference between the malignancy risk of slightly suspicious (2, 3, and 4a - 5%) and highly suspicious (4b and 5 - 48.5%) nodules, p < 0.001. Nodule rates for Bethesda categories I; II; III; IV; V, and VI were 9.8%; 73.1%; 6.1%; 5%; 3.3%, and 2.8% respectively. Their corresponding malignancy risks were 2-15%; 1-8%; 13-35%; 24-33%; 57-77%, and 84-100%. A significant difference in malignancy rates was found between non-surgical (I, II, and III: 2-14%) and surgical (IV-VI: 49-65%) nodules, p < 0.001.
Conclusion: Institutional prevalence of malignant nodules within benign TIRADS categories was higher than expected, whereas within suspicious TIRADS categories it was lower. Concerning Bethesda categorization, institutional prevalence of malignant nodules within benign/ indeterminate categories was greater than expected. These techniques have proven beneficial for pre-surgical triage of thyroid nodules, as shown by the steady increase in the percentage of malignant nodules within tumours operated on between 2012 and 2014.
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