CXCR4 and acute lymphoblastic leukemia: As CXCR7 expression has been reported in some hematologic malignancies, such as acute myeloid or lymphoblastic leukemia [34,35], in which CXCR4 has been described as a poor prognostic factor, it would be relevant to study if CXCR7 expression improves the CXCR4 prognostic value.