Bethesda System for Reporting Thyroid Cytopathology: Cyto-Histopathological Correlation in Thyroid Lesions.

Background: Fine-needle aspiration cytology (FNAC) is the preferred initial investigation for thyroid nodules. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) standardizes reporting, estimates the risk of malignancy, and guides clinical management. Histopathological examination remains the gold standard for definitive diagnosis. Objective: To evaluate thyroid lesions using the Bethesda System and determine the cyto-histopathological correlation and diagnostic accuracy of FNAC. Materials and Methods: This prospective observational study included 120 patients with thyroid swellings who underwent FNAC followed by thyroidectomy and histopathological examination. Cytological findings were classified according to TBSRTC and correlated with histopathological diagnosis. Diagnostic indices including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), diagnostic accuracy, and Cohen's kappa coefficient were calculated. Results: Females constituted 76.7% of patients, and Bethesda Category II (Benign) was the most common cytological diagnosis (60%). The risk of malignancy progressively increased from 4.2% in Category II to 100% in Category VI. FNAC demonstrated a sensitivity of 91.4%, specificity of 96.8%, positive predictive value of 91.4%, negative predictive value of 96.8%, and an overall diagnostic accuracy of 95%. The Cohen's kappa coefficient of 0.88 indicated excellent agreement between cytological and histopathological diagnoses (p<0.001). Conclusion: The Bethesda System provides excellent cyto-histopathological correlation and accurately stratifies thyroid nodules according to their risk of malignancy. FNAC interpreted using the Bethesda System is a highly sensitive and specific diagnostic tool that supports appropriate clinical decision-making and minimizes unnecessary thyroid surgery.