CD34 and cancer: We established epithelial and mesenchymal (stem cell, undifferentiated) subtypes by the clustering of 18 genes, including the six classical transcriptional inhibitors and epithelial–mesenchymal transition markers ZEB1, ZEB2, SNAI, SNAI2, TWIST1 and TWIST2, as well as CD34 and genes that discriminated “epithelial” and undifferentiated/mesenchymal subtypes in different cancer types [32] (Figure 3).