CXCR4 and pancreatic neoplasm: Since the surface markers CXCR4 and CD133 are not only expressed on pancreatic tumor stem cells but also on cells of the immune system and hematopoietic stem cells, respectively, molecular characterization of PaCSCs by flow cytometry techniques using CXCR4+ and CD133+ double labeling from the selection of the epithelial tumor cell population (EpCAM+) was proposed; that is by triple EpCAM+CXCR4+CD133+ labeling, eliminating a non-specific background of other false positive cell types [51,52].