Examples for suggested driver mutations are the SET-binding protein 1 (SETBP1) in atypical chronic myeloid leukemia (aCML),10,11SRSF2 in chronic myelomonocytic leukemia (CMML),12–14 and CSF3R in chronic neutrophilic leukemia.15,16 Another common diagnostic difficulty that can now be overcome using genetic information is the differentiation between primary myelofibrosis and other causes of bone marrow fibrosis. This evidence concerns the gene CSF3R and primary myelofibrosis.