In a seminal, international collaborative study (Mayo Clinic and the French CMML consortium), cytogenetic and molecular correlates were assessed in 409 patients with WHO-defined CMML.4 The mutational frequency of commonly affected genes was: SRSF2 (46%), ASXL1 (37%), U2AF1 (8%), SF3B1 (7%), and SETBP1 (4%), respectively. This evidence concerns the gene U2AF1 and chronic myelomonocytic leukemia.