A case of Philadelphia chromosome-positive acute lymphoblastic leukemia with minor BCR::ABL1 fusion detected in neutrophils at initial presentation

Abstract

We report a case of Philadelphia chromosome-positive acute lymphocytic leukemia (Ph⁺ALL) wherein the BCR::ABL1 chimeric gene was also detected in peripheral blood neutrophils at initial presentation. The patient, a 9-year-old boy, was diagnosed with minor BCR::ABL1 chimeric gene-positive Ph⁺ALL. The peripheral blood neutrophil FISH test was also positive for BCR::ABL1. Treatment commenced with multi-agent chemotherapy involving dasatinib, resulting in molecular remission. However, a molecular relapse occurred following intensified therapy, prompting the consideration of hematopoietic stem cell transplantation. In recent studies, the BCR::ABL1 chimeric gene has been detected in cell populations beyond B lymphoblasts, and the concept of “CML-Like Ph⁺ALL” with a background of chronic myeloid leukemia (CML)-like disease has been proposed. The pathogenesis of this case was considered to be consistent with this disease concept. The pathogenesis and prognosis of CML-like Ph⁺ALL remain unclear, and further accumulation of evidence and analysis of similar cases is needed to establish optimal treatment.