Correlation of Bethesda Categories in Thyroid Lesions With Histopathology: A Single Tertiary Care Center Experience.

Introduction Thyroid nodules can be identified primarily through physical examination and history; however, there is no single test to evaluate a thyroid nodule, especially to assess the risk of malignancy (RoM). Hence, a triple assessment through clinical examination, radiological imaging with Thyroid Imaging Reporting and Data System (TIRADS) scoring, and fine needle aspiration cytology (FNAC) is done. The 2023 Bethesda System of Reporting Thyroid Cytology (TBSRTC) is used for the risk stratification of thyroid lesions by FNAC, which will help in management decisions. Materials and methods This is a retrospective cross-sectional study conducted at a tertiary care center in Chennai to compare and correlate 101 thyroid histopathology cases with their corresponding cytology smears over one year. The FNAC smears were categorized into one of the six categories according to TBSRTC. The performance of the thyroid cytology was assessed by calculating parameters such as specificity, sensitivity, and RoMs. The results of the study were then compared with the established RoM in TBSRTC and published literature. Results Among the 101 cases, 65 (64.35%) were benign and 36 (35.64%) were malignant. Papillary thyroid carcinoma (PTC) was the most common type of malignant tumor with 30 cases (83% of malignancies). Out of the six Bethesda categories, Bethesda category II (benign) had the least RoM (18%), but in comparison with the established rates of TBSRTC and other published studies, it was observed to have a higher RoM. Category III (atypia of unknown significance) has 12 cases, of which three were malignant with a RoM of 25%. Category IV (follicular neoplasm) had the most discordance from histopathology and had a higher RoM (50%) than the established TBSRTC rates. The sensitivity of the current study was 68.57%.  Conclusion The current study reveals higher RoMs than published studies. Maximum concordance between histology and cytology can be achieved by avoiding aggressive aspiration techniques, a few amendments to reporting criteria, making them less subjective, and periodic quality assurance procedures to improve the accuracy of diagnosis. Moreover, assistive and adjunct methods like immunocytochemistry and molecular testing can also be used in indeterminate lesions.