Note=A chromosomal aberration involving FGFR1OP2 may be a cause of stem cell myeloproliferative disorder (MPD). Insertion ins(12;8)(p11;p11p22) with FGFR1. MPD is characterized by myeloid hyperplasia, eosinophilia and T-cell or B-cell lymphoblastic lymphoma. In general it progresses to acute myeloid leukemia. The fusion protein FGFR1OP2-FGFR1 may exhibit constitutive kinase activity and be responsible for the transforming activity.