Diagnostic Efficacy of Fine Needle Aspiration Cytology and Cell Block Technique in Thyroid Lesions: A Hospital-based Study

Introduction: Fine Needle Aspiration Cytology (FNAC) and Cell Block are very commonly used initial tests for triaging thyroid lesions and play a pivotal role in deciding subsequent clinical management of thyroid nodules. In most cases, after excision, the diagnosis remains unchanged, but at times discordance does occur when benign lesions are reported on FNAC and cell blocks are found to be malignant on final histopathology and vice-versa. Aim: To assess the diagnostic efficacy of both FNAC and Cell Block technique in the evaluation of thyroid lesions by comparing their respective results with final histopathological diagnosis (after excision) in case of malignancies and clinico- radiological follow-up in benign cases. Materials and Methods: An observational hospital-based study was conducted in the Department of Pathology in a Tertiary Care Teaching Institute from 1st November, 2016 to 31st October, 2017. A total of 100 cases of thyroid masses were subjected to both FNAC and Cell Block and the diagnostic efficacy of both the techniques was assessed using MedCalc Statistical Software. Results: Mean age of the patients was 42.75±15.75 years with a range of 12-75 years. Females constituted 88% of the sample with male to female ratio of 1:7.3. 88% lesions were benign, 8% were malignant and 4% suspicious of malignancy on conventional smears in comparison to cell block which showed 90% benign, 8% malignant and 2% suspicious lesions. The validity of FNAC in terms of sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) and accuracy was found to be 100%, 95.65%, 66.67%, 100.00% and 96.00% respectively, whereas for cell blocks these statistics were 100%, 97.83%, 80%, 100% and 98% respectively. Conclusion: Cell block improved the overall diagnostic accuracy of FNAC when used as an adjunct leading to 100% diagnostic yield. The results of this study also establish that FNAC and Cell blocks are sensitive, specific, and accurate as preliminary diagnostic tests for evaluation of patients with thyroid swellings. Moreover, their combined use can reduce the diagnostic errors and to improve the overall reporting efficacy. It is thus advised to perform cell block for each case of FNAC in thyroid lesions.