This Japanese nationwide survey analyzed patients with AML (n = 22) and mixed phenotype acute leukemia (MPAL) (n = 10) with t(9;22) or BCR::ABL1 who underwent allogeneic hematopoietic cell transplantation (allo‐HCT) between 2002 and 2018. The gene discussed is ABL1; the disease is acute leukemia.