Background and Objective: The objective of current study aimed (i) to analyse the thyroid cytology smears by the Bethesda system, (ii) to determine the distribution of diagnostic categories, (iii) to stratify the malignancy risk, (iv) to correlate cytopathology with histopatholgy, whenever surgery was done.
Material and method: This is a prospective study of 600 Fine needle aspiration cytology (FNAC) of thyroid nodules which were classified according to the Bethesda system and 119 histological evaluation obtained from this group. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy rates were evaluated.
Result: The distribution of various categories were: Nondiagnostic/Unsatisfactory (ND/UNS) 11 (1.8%), Benign 495 (82.5%), Atypia of undetermined significance/Follicular lesion of undetermined significance (AUS/FLUS) 26 (4.3%), Suspicious for follicular neoplasm (SFN) 18 (3%), Follicular neoplasm of Hurthle cell type (FNHCT) 3 (0.5%), Suspicious for malignancy (SM) 8 (1.3%), and malignant 39 (6.5%). In 119 cases, there was follow up histology. The implied malignancy risk in these categories were: 16.6%, 3.5%, 18.18%, 14.28%, 60% and 100% respectively. The sensitivity, specificity, accuracy, PPV and NPV were 75.4%, 60.3, 96.4%, 94.11% and 72% respectively.
Conclusion: We recommended routine ues of Bethesda system for reporting Thyroid cytopathology (BSRTC) for initial workup of patients with thyroid nodule. However risk of malignancy was found to be significantly high in Bethesda III category to warrant further workup including ultrasonography/ thyroid scan in addition to repeat FNAC. It also provides clear management guidelines to the clinicians to go for follow up FNA or surgery and also extent of surgery.
