This trial includes patients with chronic lymphocytic leukemia, the most common kind of malignant lymphoma. Monoclonal antibodies directed against cluster of differentiation antigen 20 have improved treatment results in different forms of lymphomas; however in chronic lymphocytic leukemia treatment with monoclonal antibodies is less effective, and it has been suggested that this is depending on a lower expression of the cluster of differentiation antigen 20 protein on the chronic lymphocytic leukemia cells.