We conclude that some of the tumour cells have the double-positive keratin phenotype of the ERα/BMI1 cells grown in vitro (Figure 1g), whereas others differentiate to single-positive cells that may represent a step of differentiation towards a luminal or myoepithelial fate, but with a strong tendency for the latter to progress to asquamous phenotype. This evidence concerns the gene ESR1 and neoplasm.