CD33 and chronic myelogenous leukemia, BCR-ABL1 positive: CD33 is a myeloid differentiation antigen which is predominantly expressed on the cell surface of leukocytes of the myeloid lineage and with high frequency on myeloid leukemia cells, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML) and myelodysplastic syndrome (MDS) [31–35].