While the characteristic immunophenotype of CLL and CLL-type MBL includes expression of CD19, CD20, CD5 and CD23, frequently accompanied by CD43, CD79b, CD81, CD200 and ROR1, the absolute B-cell count defines the specific subgroup [13, 24]: A count below 0.5 × 10^9 /L outlines low-count MBL, which comprises a clonal B-cell expansion commonly found in the elderly population. This evidence concerns the gene CD81 and B-cell chronic lymphocytic leukemia.