Clinical and laboratory parameters that define clinically relevant B-CLL subgroups.

B cell-type chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease. This is reflected by the very wide-ranging clinical courses that B-CLL patients experience and by the marked variation in laboratory findings between patients. In this chapter, we will review the various clinical and laboratory parameters that divide B-CLL patients into "subgroups," and correlate the parameters that define them. When feasible, we will also link clinical features to the cellular and genetic characteristics recently defined for these leukemic cells. The discussion is limited to parameters that define phenotypes or subgroups that may relate to disease activity and clinical outcome.