Keratin expression in breast cancers.

Cytokeratin (CK) immunohistochemistry can play an important role in breast carcinoma evaluation. We evaluated the expression of a panel of commonly used CKs in a large cohort of breast cancers and assessed its correlation with other biomarkers and breast cancer subtypes. Expression of CK7, CK8, CK18 and CK19 was observed in more than 90 % of all breast carcinomas in this study, confirming their efficacy in immunohistochemical identification of breast cancer. A combination of CK8 and CK7 gave the highest sensitivity for detection of a minute number of breast cancer cells. Expression of other CKs, including CK5/6, CK14 and CK20, correlated positively with high tumour grade. The expression of CK5/6 and CK14 in a significant number of high-grade tumours raised concern regarding the use of absence of their expression to identify breast carcinoma. For identification of the basal subtype, CK5/6 gave a higher detection rate than CK14. CK20 expression was found more frequently than reported in previous studies, might constitute an indicator of poor prognosis and may be associated with the molecular apocrine subtype. This study highlights the diagnostic and prognostic relevance of the unique CK expression patterns in breast cancer.