In the present case, the characteristic cytomorphological features, the myeloid immunophenotype of the blast cells with distinct maturation patterns and positivity for CD25 and CD123, along with the absence of the Philadelphia chromosome and the c-kit D816V mutation favored a diagnosis of ABL and ruled out basophophilic blast crisis of CML, acute lymphoblastic leukemia, non-basophil lineage AML, AML with t(6;9)(p23;q34) (13) and mast cell leukemia. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.