Immunohistochemical analysis of cytokeratin #8 as a prognostic factor in invasive breast carcinoma.

Cytokeratin #8 (CK8) was analysed by immunohistochemistry using a monoclonal antibody in 101 operable invasive breast carcinomas (IBCs). The immunohistochemical staining pattern, and its correlations with patient characteristics and prognosis were studied. Sixty-five (65%) out of 101 patients had CK8 positive tumors. The incidence of CK8 positivity in patients with estrogen receptor (ER) positive tumors was significantly higher than that in patients with ER negative tumors. The same tendency was seen between the CK8 positivity and progesterone receptor (PR) status; however, no statistical significance was found. Furthermore, the incidence of CK8 positivity in premenopausal patients was lower than that in postmenopausal patients with no statistical significance. Relapse-free survival (RFS) for patients with CK8 positive tumors was significantly better than that for patients with CK8 negative tumors. The multivariate analysis of factors related to RFS showed that CK8 staining positivity was an independent prognostic indicator of IBCs. These results suggest that CK8 expression may be one of the prognostic factors of IBCs.