In CP CML, LSC are thought to originate in the CD34+ CD38− fraction of HSC [20,21] or from the primitive hemangioblast, whilst in BP CML and acute myeloid leukemia LSC may arise in HSC or in more committed cells of the hematopoietic hierarchy [21] (Figure 1A). Here, CD34 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.