The presence on peripheral blood of ≥5000 lymphocytes/μL with the typical immunophenotypic co-expression of T cell marker CD5 and B cell surface antigens CD19, CD20, and CD23 with low levels of monoclonal immunoglobulin defines CLL diagnosis according to the international working group of CLL [3,4]. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.