Immunohistochemical Expression of Cytokeratin 19 in Patients with Papillary Thyroid Carcinoma and its Mimics in Erbil, Kurdistan Region, Iraq

Abstract

Background and objective: Papillary thyroid carcinoma (PTC) is the most common primary thyroid cancer. PTC diagnosis is based on the presence of classic nuclear features in most cases. However, there are some mimics including both benign neoplastic and non-neoplastic lesions, therefore immune-histochemical stains are necessary for equivocal cases. This study aimed to evaluate the diagnostic expression of CK19 in different thyroid lesions and also to differentiate PTC from other mimicking thyroid lesions. Methods: A retrospective study of 90 cases of different thyroid lesions (56 patients with benign neoplastic and non-neoplastic lesions and 34 PTC) was investigated from January 2018 to January 2020. Immunohistochemical staining with CK19 was performed. Results: CK19 IHC expressed in about 94% of PTC cases as moderate and strong pattern of staining, while in benign neoplastic and non-neoplastic thyroid lesions only 7% expressed as moderate and non with strong pattern of staining, it showed a significant statistical difference (P <0.001).The sensitivity and specificity of CK19 total estimated score for diagnosis of PTC were 94.1% and 92.9%, respectively. Conclusion: Although no single immunohistochemical marker is completely sensitive in differentiating benign from thyroid malignancy, this study found a significant and effective role of CK19 in distinguishing PTC from benign neoplastic and non-neoplastic mimickers’ lesions. In addition, lymph node metastatic tumor cells retained the same staining intensity of CK19.