While CLL has not been formally classified into subgroups, the division of B-CLL into stable and progressive disease was noted in the 1960's, and it is now generally agreed that there are two subsets of CLL based on IgVH gene mutational status. (see also: What is the significance of IgVH gene mutational status in CLL?)
As we learn more about CLL and as more sophisticated techniques become available for studying CLL at a molecular level, formal subgroups may be identified. This, in turn, may help to explain why CLL progresses very differently among patients and why response to treatment can vary widely. Some differences in disease progression and response to treatment are no doubt attributable to patient differences such as age and general health, but we may find that additional differences in CLL also exist.