KRT5 and breast cancer: Invasive breast cancers expressing the basal epithelial phenotype, based on the consensus of the published literature from cDNA microarray and IHC analyses, are ERα negative (Perou et al, 2000; Sorlie et al, 2001; Vijver et al, 2002; Nielsen et al, 2004; El-Rehim et al, 2005), CK5/6 positive (Sorlie et al, 2001; Korsching et al, 2002; Nielsen et al, 2004; Collett et al, 2005) and/or CK14 (El-Rehim et al, 2005) positive.