KRT5 and breast cancer: The majority of sporadic breast cancer cases originate from luminal epithelial cells, and this finding is supported by morphological, biochemical and molecular evidence.4,5,7,8 A previous study carried out by our group showed that it is possible to characterize a basal breast cancer phenotype using the following markers: p63, cytokeratin 5 (CK5) and p-cadherin (p-cad).9 Essentially, cytokeratins 5 (CK5), 6 and 14 are recognized as basal forms of cytokeratin, whereas cytokeratins 8, 18 and 19 are expressed by glandular or luminal cells.10,11