Categorization of Thyroid FNAC Using the Bethesda System and Its Histopathological Correlation

Abstract

BackgroundThyroid nodules are common endocrine lesions, with the primary clinical challenge being the identification of malignancy among predominantly benign cases. Fine-needle aspiration cytology (FNAC), reported using the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), provides standardized risk stratification; however, its diagnostic performance requires validation through histopathological correlation.MethodsThis observational study was conducted over two years at a tertiary care center. A total of 122 patients with thyroid swelling underwent FNAC, of which 83 had subsequent histopathological follow-up. Cytological findings were categorized according to TBSRTC. Cytohistopathological correlation was performed, and the risk of malignancy (ROM) was calculated for each category. The diagnostic performance parameters, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy, were determined using histopathology as the reference standard.ResultsThe majority of cases were categorized as Bethesda Category II (81.15 %). Histopathological examination revealed that 83.13% of the lesions were non-neoplastic and 16.87% were neoplastic, with papillary carcinoma being the most common malignancy. The concordance rates were 89.86% and 78.57% for non-neoplastic and neoplastic lesions, respectively. The ROM increased progressively from Category I (0%) to Category VI (100%). FNAC demonstrated a sensitivity of 78.57%, specificity of 89.85%, PPV of 61.11%, NPV of 95.38%, and an overall diagnostic accuracy of 87.95%.ConclusionFNAC, when interpreted using the Bethesda system, is a reliable and effective initial diagnostic modality for thyroid nodules. Cytohistopathological correlation enhances diagnostic accuracy and highlights the limitations of indeterminate categories. Standardized reporting using the TBSRTC facilitates appropriate clinical management and reduces unnecessary surgical interventions.