Overall, our results confirm previous reports on the prevalence of JAK2 mutations in PV, ET, CML, and MDS (Jones et al., 2005) and suggests that the JAK2 V617F mutation is common in MPD’S as well in hematological disorders, although the occurrence of JAK2 V617F mutation in leukemic patients is less compared to PV and ET (Jones et al., 2005; Steensma et al., 2005). This evidence concerns the gene JAK2 and essential thrombocythemia.