Overexpression of cytokeratin 17 is associated with the development of papillary thyroid carcinoma and the presence of lymph node metastasis

Cytokeratin 17 (CK17), a basal/myoepithelial cell keratin, appears to play an important role in the progression of several human malignancies. Increased CK17 expression has previously described in cases of papillary thyroid carcinoma (PTC). However, no studies to date have investigated the clinical significance of CK17 expression in patients with PTC. The aim of this study was to compare the expression of CK17 in patients with PTC with that observed in normal thyroid tissue and benign thyroid lesions, and to examine the relationship between CK17 expression and clinicopathologic characteristics of patients with PTC. CK17 protein expression was evaluated by immunohistochemistry on tissue microarrays containing thyroid tissue samples from 108 PTCs, 16 nodular goiters, and 81 healthy controls. Sixty-five of the 108 (60.2%) PTC tissue samples exhibited positive CK17 expression, whereas all nodular goiters and normal thyroid tissue samples showed a complete absence of CK17 immunoreactivity. The difference in frequency of CK17 positivity between PTC (65/108, 60.2%), normal thyroid tissue (0/81, 0.0%), and benign thyroid lesions (0/16, 0.0%) was statistically significant (P<0.001). Positive CK17 expression in PTC was significantly associated with the presence of lymph node metastasis (P=0.024) and higher pN stage (P=0.028). Expression of CK17 is significantly increased in cases of PTC compared to normal tissue and benign thyroid lesions, and CK17 overexpression is associated with the presence of lymph node metastasis in patients with PTC. These findings suggest that CK17 is involved in the development and metastasis of PTC.