Fine Needle Aspiration Cytology of Thyroid Lesions Using Bethesda Classification and Histopathological Correlation

Abstract

ABSTRACT Background: To keep uniformity and to achieve standardization of thyroid cytopathology reporting National Cancer Institute proposed six tier diagnostic classification system named The Bethesda system for reporting thyroid cytopathology (TBSRTC) that represents a major step toward standardization, reproducibility, and ultimately improved clinical significance, usefulness, and predictive value of thyroid Fine-needle aspiration cytology (FNAC). The guidelines were formulated in 2007 and revised in 2017. Material and Methods: The present study was performed at between January 2015 and June 2019, on thyroid FNA classifying them according to TBSRTC. Cytology and histopathology correlation were done where ever available. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of TBSRTC were calculated considering histopathology as gold standard. The malignancy risk for each category was calculated and the result was tabulated. Results: In the present study, total of 1248 cytology cases of thyroid were studied, out of them 1% were non diagnostic, 91.3% were benign, 1.5% were atypical lesions of undetermined significance (AUS). About 4% were follicular neoplasm (FN), 0.4 was suspicious for malignancy (SM), and 1.8% were malignant. A total of 179 cases were available for cytology and histopathology correlation and risk of malignancy (ROM) was calculated. No histopathology cases were available in category I for correlation, ROM was 4.7% in benign category, 46.2% in AUS category, 50% in SFN/FN, 100% in SM, and 85.7% in malignant category. TBSRTC showed sensitivity of 66.7%, specificity of 90.9%, PPV of 64.8%, NPV of 91.5%, and accuracy of 86.03%. Conclusion: TBSRTC improves perceptions of diagnostic terminology between cytopathologists and clinicians, prevent over diagnosis and helps in better patient management approaches. It should be included in all FNAC of thyroid reporting system.