CXCR4 and plasma cell myeloma: The role of CXCR4/CXCL12 axis has been proved also in hematopoietic neoplasms, such as acute lymphoblastic leukemia (ALL) [8], [9], acute myeloid leukemia (AML) [10], chronic lymphocytic leukemia (CLL), multiple myeloma (MM) and Waldenström Macroglobulinemia (WM) [11].