Cytokeratin19 expression discriminates papillary thyroid carcinoma from other thyroid lesions and predicts its aggressive behavior.

Cytokeratin19 (CK19) has been reported as a useful marker of thyroid tumors. We evaluated its value for differential diagnosis of thyroid neoplastic lesions and assessed its usefulness for predicting aggressive behavior of papillary thyroid carcinomas by correlating immunohistochemical results with clinicopathological features of the patients. A total of 351 thyroid tissue samples included 27 follicular adenomas (FTA), 18 follicular carcinomas (FTC), 147 papillary carcinomas (71 of follicular type-PTCfv and 76 of classical type-PTCcl) and 33 cases of anaplastic carcinoma with 126 adjacent thyroid tissues. Diagnostic usefulness of CK19 was determined by ROC analysis, while its value as a predictive marker of PTC was tested by univariate and multivariate analysis. According to ROC analysis, CK19 can discriminate both types of PTC from other neoplasias of the thyroid gland (p < 0.05). Although greatest accuracy was gained for the identification of PTCcl (91.07 %), this marker was also helpful for distinguishing PTCfv from FTA and FTC (accuracy 71.43 and 65.17 %, respectively). Regarding the univariate set of tests, high expression of CK19 correlated significantly with age, multifocality, extrathyroidal extension, pT status and pTNM stage of PTC (p < 0.05 for all). Multivariate analyses confirmed the significant association of high CK19 expression with extrathyroidal extension of PTC as well as with pTNM stage (p < 0.05 and p < 0.01, respectively). CK19 is a useful marker for the identification of both types of PTC. High expression of this protein predicts the aggressive behavior of PTC and can help in the identification of a particular subgroup of PTC patients with a potentially worse prognosis.