We chose 4 acute myeloid leukaemia (AML) patients, 4 chronic myeloid leukemia (CML) patients, 4 acute lymphoblastic leukemia (ALL) patients, 3 myeloproliferative neoplasm (MPN) patients, 3 polycythemia vera (PV) patients, 2 essential thrombocythemia (ET) patients and 2 healthy volunteers to evaluate the expressions of CD44. This evidence concerns the gene CD44 and acquired polycythemia vera.