Basal cytokeratin expression in relation to immunohistochemical and clinical characterization in breast cancer patients with triple negative phenotype.

AIMS AND BACKGROUND To evaluate the immunohistochemical characterization of CK5/6 and CK17 and whether the expression level of the two markers was correlated with clinical outcome or pathological feature in triple negative (ER-, PR-, HER-2-) patients with breast cancer. METHODS AND STUDY DESIGN We carried out an immunohistochemical assay for CK5/6 and CK17 markers on formalin-fixed invasive carcinoma samples from 112 patients who were diagnosed between 2000 and 2002. All of them had an immunohistochemical triple negative status and follow-up information available. RESULTS Of the 112 patients characterized by triple negative immunohistochemical status, 82 (73.2%) were disease free with no relapse or metastasis. In total, CK5/6 and CK17 were both determined positive in 33.9% (38/112) of the 112 tumor samples, and 46.4% (52/112) were regarded as positive for CK5/6 or CK17. The Kaplan-Meier curve showed that positive staining for CK5/6, CK17, or CK which means CK5/6 positive or CK17 positive, was associated with worse disease-free survival (P = 0.020, P = 0.032, P = 0.003), and positive staining for CK5/6 or CK was associated with worse overall survival (P = 0.027, P = 0.015). When we considered 91 patients whose pathological type was invasive ductal carcinoma, we found that there was also an association between CK5/6 or CK17 immunostaining and high grade (P = 0.030). In addition, these two markers were also associated with axillary lymph node status (P = 0.044). The Cox regression multiple-factor analysis showed that pathological stage, grade and expression of CK were the factors affecting both disease-free and overall survival, whereas age and menopausal status were independent factors affecting disease-free and overall survival, respectively. CONCLUSIONS; Positive staining for CK5/6 or CK17 was associated with a worse prognosis, high tumor grade and positive axillary lymph nodes.