Immunohistochemistry of the tumor-associated cells showed CD5 (+), CD20 schistose dim (+), PAX-5 (+), CD23 (+), LEF-1 (+), CD200 partial (+), Ki-67 (5%), CD3 (−), CD10 (−), Cyclin-D1 (−), SOX-11 (−), CD138 (−), Kappa (−), and Lambda (−), consistent with CLL (B-CLL; tumor cells accounted for about 70%; MF-1 grade). This evidence concerns the gene PAX5 and B-cell chronic lymphocytic leukemia.