NRAS encodes a membrane protein GTPase that is a central mediator of downstream growth factor receptor signaling, critical for cell proliferation and survival. Mutations in codons 12, 13, and 61 of NRAS have been reported in 7-22% of acute myeloid leukemia, 12% of chronic myelomonocytic leukemia, 20% of blastic plasmacytoid dendritic cell neoplasm, 16% of juvenile myelomonocytic leukemia, 4-10% of myelodysplastic syndromes, and 5% of primary myelofibrosis. In addition, NRAS mutations have been described in approximately 15% of cases of B-ALL and, interestingly, some cases of ALL may show more than one abnormality in the RAS pathway. NRAS mutations are associated with an unfavorable prognosis in chronic myelomonocytic leukemia and primary myelofibrosis. NRAS mutations are also associated with an unfavorable prognosis in myelodysplastic syndrome, particularly in patients predicted to have lower-risk myelodysplastic syndrome (NCCN Guidelines for Myelodysplastic Syndromes). NRAS mutations do not seem to have significant prognostic impact in AML.