Bipotent precursor cells present in mammary stem/progenitor cells and breast TICs/cancer stem cells have been characterized by coexpression of luminal epithelial cytokeratin 18 (K18)/K8 markers and myoepithelial cytokeratin 14 (K14)/α-smooth muscle actin (SMA) markers [21]–[29]. Here, KRT18 is linked to cancer.