The term “basal-like” was introduced in 2001 (Sorlie et al., 2001) to refer to a group of human breast cancers that share an RNA signature that includes a high expression of cytokeratins 5 and 17 (CK5 and CK17), laminin, and fatty acid binding protein 7; i.e., proteins found in basal cells but not luminal cells of the normal human mammary gland. Here, KRT5 is linked to breast cancer.