JAK2 and myeloproliferative disorder: Chronic myeloid neoplasms are in turn classified into four operational categories: myelodysplastic syndromes (MDS), MPNs, MDS/MPN overlap and myeloid/lymphoid neoplasms with eosinophilia and recurrent rearrangements of PDGFRA, PDGFRB, and FGFR1 or PMC1-JAK2; the latter mutations correspond to 5q33, 4q12, 8p11.2 or t(8;9)(p22;p24.1) cytogenetic abnormalities, respectively.