Chronic lymphocytic leukemia (CLL) is characterized by the expansion of monoclonal, mature CD5+/CD23+ B cells in the peripheral blood (PB) [1], secondary lymphoid tissues, and the bone marrow (BM).In this microenvironment CLL cells receive survival, proliferation and drug resistance signals from accessory cells and soluble factors [2]. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.