In a first report, Maxson and colleagues found CSF3R mutations in 59% of patients with CNL or aCML, while subsequent analysis indicated that the activating CSF3R T618I mutation is present in < 10% of cases of aCML [11, 69, 70]. The gene discussed is CSF3R; the disease is atypical chronic myeloid leukemia, BCR-ABL1 negative.