DIAGNOSTIC ACCURACY OF BETHESDA SYSTEM FOR REPORTING THYROID CYTOLOGY WITH HISTOPATHOLOGICAL CORRELATION

Abstract

Background: Fine Needle Aspiration Cytology (FNAC) is a widely accepted, minimally invasive, and cost-effective diagnostic tool for evaluating thyroid nodules. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) standardizes thyroid cytology reporting and provides an estimated risk of malignancy for each diagnostic category. Aim: To assess the diagnostic accuracy of the Bethesda System for Reporting Thyroid Cytopathology by correlating cytological findings with histopathological diagnoses. Materials and Methods: This retrospective cross-sectional study was conducted in the Department of Pathology, Adesh Medical College and Hospital, Shahbad. A total of 100 patients who underwent both thyroid FNAC and subsequent histopathological examination between August 2023 and September 2025 were included. FNAC findings were categorized according to TBSRTC and correlated with histopathological diagnoses. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), diagnostic accuracy, and risk of malignancy (ROM) for each Bethesda category were calculated. Results: The majority of patients were females (78%), with the highest incidence observed in the 31–40-year age group (28%). Bethesda Category II constituted the largest proportion of cases (85%), followed by Category IV (6%), Category VI (5%), Category V (3%), and Category III (1%). No Category I cases were encountered. The risk of malignancy was 2.4% for Category II, 33.3% for Category IV, 80% for Category V, and 100% for Category VI. Cyto-histopathological correlation demonstrated 5 true-positive, 90 true-negative, and 5 false-negative cases, with no false-positive cases. FNAC showed a sensitivity of 50%, specificity of 100%, PPV of 100%, NPV of 94.7%, and overall diagnostic accuracy of 95%. Conclusion: The Bethesda System is a reliable and effective reporting framework for thyroid cytology. FNAC demonstrated excellent specificity, high negative predictive value, and high overall diagnostic accuracy, supporting its role as a first-line investigation for thyroid nodules. Cyto-histopathological correlation remains essential for quality assurance and improving diagnostic performance, particularly in indeterminate and false-negative cases.