KRT19 and neoplasm: Whereas iHBECERpos under these conditions behaved like EpCAMhigh/CD271low/CD166high/CD117low primary cells and readily formed correctly polarized K19+/K14- acini in the presence of TGFβR inhibitors, and in the presence of estrogen, branching structures, MCF7 formed tumor-like nests of cells without appreciable polarization (Figure 6).