 These sub-groups can be identified by either the presence or the absence of mutations in antibody genes andor by the percentage of B-CLL cells expressing a particular protein called CD38. These two sub-groups unmutated antibody genes high percent CD38 and mutated antibody genes low percentage CD38 follow strikingly clinically different courses. For example, the unmutatedCD38 group experiences a much more aggressive disease and these patients almost invariably die much sooner than the cases in the other group. In addition, the patients in the mutated CD38 group require much more chemotherapy than mutatedlCD38-. Finally, surprisingly there is a much higher representation of males in the poor outcome unmutated CD38 group than in the better outcome group. The reasons for these differences in clinical outcome and gender bias are unknown. 