CD34 and leukemia: Previous studies also have shown that the c-Mpl-del isoform which encompasses a 24 amino acid deletion between exons 8 and 9 in the extracellular region was detected in CD34+ cells, megakaryocytes, and platelets isolated from healthy donors and essential thrombocythemia (ET) patients as well as megakaryocytic leukemia cells [27–29].