Although there is no generally recognised definition of the categories for stratification into intrinsic subgroups (different studies using various markers such as CK5, CK14, CK17, EGFR, KIT, p63 and smooth muscle actin (Nagle et al, 1986; Wetzels et al, 1991; Malzahn et al, 1998; Tsuda et al, 1999; van de Rijn et al, 2002; Abd El-Rehim et al, 2004; Matos et al, 2005; Fulford et al, 2006) to identify basal-like tumours), in this study we have used the classification developed by Nielsen et al (2004). The gene discussed is KRT5; the disease is neoplasm.