Case 1 is unique in the following: (1) she presented as T-ALL with BCR-ABL1 rearrangement, but has some concurrent morphologic features of background CML: myeloid hyperplasia with left-shift, mild basophilia, and small, hypolobated megakaryocytes; (2) her relapsed marrow biopsies never showed morphologic features of CML; (3) her remission marrow biopsies never demonstrated features of CML-CP or a karyotype with t(9;22). Here, ABL1 is linked to acute lymphoblastic leukemia.