Ascertaining the role of cytokeratin-19 (CK19) and its staining pattern helps to differentiate papillary carcinoma from other thyroid lesions. To correlate fine needle aspiration cytology (FNAC) and cell block study of equivocal cases (Category III, IV, and V) with the role of CK19 staining in it. A hospital-based cross-sectional observational study was designed and conducted at North Bengal Medical College and Hospital, Shusrutnagar, Darjeeling. The FNAC performed and reported as per TBSRTC-2017.50 cases of Category III, IV, and V was selected for cell block study and CK19 staining followed by immunohistochemical scoring. Out of 50 cases, 17 were follicular neoplasm, 21 papillary carcinoma, 6 lymphocytic thyroiditis, 1 Hürthle cell adenoma, 1 medullary carcinoma, 1 lymphoma, and 3 undifferentiated carcinomas. Among cases of papillary carcinoma, 10 showed 4+ positivity, 9 showed 3+ positivity, 2 showed focal 1+ and 2+ positivity. In the case of follicular neoplasm, 1 showed 3+ positivity, 3 cases had 1+ 2+ positivity, and 13 cases revealed negative staining. Role of CK19 in distinguishing papillary carcinoma of thyroid from other lesions in cytologically diagnosed Category III, IV, and V (TBSRTC-2017) cases can be demonstrated.