KRAS and atypical chronic myeloid leukemia, BCR-ABL1 negative: Mutations in the KRAS and NRAS genes are frequently identified, with mutations in NRAS more frequent than mutations in KRAS, in myeloid disorders (15%–60%), including acute myeloid leukemia (AML), atypical chronic myeloid leukemia (aCML), CMML, and JMML (12).