Utility of the Dynamic Duo of Ck19 and Cd56 in Cytological Diagnosis of Thyroid Nodules

Purpose: Thyroid nodules are a common finding in everyday clinical practice, however only a small percentage is malignant. A cytologic examination is directed toward establishing a precise diagnosis to distinguish malignant or suspicious nodules requiring surgical treatment from those that can be medically managed. Fine-needle aspiration (FNA) is the first choice for diagnostic evaluation of thyroid nodules. It can be a screening test for a large population of patients with nodules, a small group of whom should be considered for surgery. Various ancillary tests have been proposed to help more accurately classify thyroid FNA to prevent unnecessary surgery.The present study was undertaken to evaluate utility of immunoexpression of CK19, and CD56 in the diagnosis of thyroid nodules. Methods: This was a prospective study conducted over a period of 4 years, in tertiary care referral hospital from 2014 August to 2018. A total of 108 cases were included in the study and the fine needle aspiration cytology smears were subjected to CK19, CD56 immunocytochemistry in 98 cases for evaluation based on adequacy criteria. Results: CD56 expression was lost in 96.29% of papillary thyroid carcinomas with a sensitivity of discriminating malignant from benign thyroid lesion was 83.87% and specificity of 94.44%. CK19 expression in PTCs with a sensitivity of 92.0% and specificity of 83.3% was noted. Conclusion: CK19 and CD56 are useful in differentiating benign and malignant thyroid neoplasms, particularly true for differentiating papillary thyroid carcinoma and benign thyroid lesions. Thus, combination of positive marker (CK19) and negative marker (CD56) increases the accuracy of diagnosis of malignancy in cytology with immunocytochemistry.