The majority of MBL cases (75%) have the immunophenotype of chronic lymphocytic leukemia (CD19(+), CD5(+), CD23(+), CD20dim⁡, and sIgdim⁡) and are classified as typical CLL-like MBL, while the remaining MBL cases are classified as atypical CLL (CD5(+) clonal population not meeting the criteria for typical CLL and not meeting the criteria for mantle cell lymphoma) and as CD5(−) non-CLL MBL [4, 5, 8]. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.