Flow cytometry of peripheral blood lymphocytes showed a clonal B-cell population (CD20+, CD79b+, CD5+, CD23+, CD43+, CD11c-, FMC7-/+, CD38-, ZAP-70 29%, ck/cλ = 66) consistent with CLL (CLL score 4). This evidence concerns the gene MS4A1 and B-cell chronic lymphocytic leukemia.