In hematological malignancies high expression of CXCR4 is observed in several entities ranging from acute leukemias such as acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) to a variety of malignant lymphomas including chronic lymphocytic leukemia (CLL), diffuse large B cell lymphoma (DLBCL), follicular lymphoma (FL), marginal zone lymphoma (MZL), multiple myeloma (MM), hairy cell leukemia (HCL) and mantle cell lymphoma (MCL) [27–32]. This evidence concerns the gene CXCR4 and hairy cell leukemia.