In hematologic neoplasms, the discovery of SETBP1 as a new oncogene has helped to better define the molecular characteristics of pathologies such as atypical Chronic Myeloid Leukemia (aCML), a disease initially defined only by negative characteristics, like the absence of BCR-ABL1 fusion. The gene discussed is SETBP1; the disease is atypical chronic myeloid leukemia, BCR-ABL1 negative.