Additional sex combs-like 1 (ASXL1) mutations have been described in all forms of myeloid neoplasms including chronic myelomonocytic leukemia (CMML) and associated with inferior outcomes, yet the molecular pathogenesis of ASXL1 mutations (ASXL1-MT) remains poorly understood. This evidence concerns the gene ASXL1 and chronic myelomonocytic leukemia.