Aims: To assess the expression of cytokeratin (CK) 5/6 in bilateral breast cancers and to assess the relationship between its expression and other prognostic variables, as well as between CK5/6 expression and patients' survival.
Methods and results: The expression of CK5/6, PTEN protein, oestrogen receptor, progesterone receptor, p53 and c-erbB-2 protein were evaluated by immunohistochemistry in 88 primary breast cancers diagnosed in 44 women. To assess the prognostic value of studied factors, Cox regression analysis was performed. Expression of CK5/6 was found in 23 of 88 primary breast carcinomas (23/88; 26%). The hazard ratio of development of distant metastasis in patients in whom at least one cancer was CK5/6+ was 99.8 (P=0.037) and in patients with at least one carcinoma with reduced PTEN expression it was 10.8 (P=0.044). CK5/6 expression was correlated with absence of oestrogen (P<0.0001) and progesterone receptors (P<0.0001) and very strong expression of p53 (P<0.05). Reduced PTEN expression was correlated with presence of axillary metastases (P<0.01), with very strong expression of c-erbB-2 (P<0.05) and with reduced expression of oestrogen receptor (P<0.05).
Conclusions: Analysis of expression of CK5/6 and PTEN protein in bilateral breast carcinomas may be of value in clinical practice and warrant further studies.