JAK2 and primary myelofibrosis: Several JAK2 fusions have been reported in leukemia/lymphoma without marked lineage preference: BCR-JAK2 in atypical chronic myeloid leukemia (CML), acute myeloid leukemia (AML) and B-cell acute lymphoblastic leukemia (B-ALL); ETV6-JAK2 in pre-B/T-ALL and CML; NFE2-JAK2 in myelodysplastic syndromes (MDS); PAX5/STRN3-JAK2 in childhood ALL; PCM1-JAK2 in myeloid, B-cell and T-cell neoplasias; RPN1-JAK2 in chronic idiopathic myelofibrosis; SEC31A-JAK2 in classical Hodgkin lymphoma; and SSBP2-JAK2 in pre-B ALL [1].