PBX1 and acute lymphoblastic leukemia: Gene cd34 encodes protein that may participate in the attachment of stem cells to the bone marrow extracellular matrix or to stromal cells, and has been associated to outcomes of acute myeloid leukaemia (AML),23, 24 but its relevance to ALL, especially to the subtype TCF3‐PBX1, remains controversial.25, 26