ABL1 and atypical chronic myeloid leukemia, BCR-ABL1 negative: Besides the lack of the Philadelphia chromosome and the BCR-ABL1 translocation, the major criteria that distinguish aCML from BCR-ABL1-positive CML are the dysgranulopoiesis, which is common in aCML but only occasionally reported in classical CML, and the normal basophil counts of the former (<2% of leukocytes) (1).