ZAP70 and B-cell chronic lymphocytic leukemia: Despite the fact that CLL is a heterogeneous disease with a variable clinical course, the data suggest that the course of CLL disease can be divided by the presence or absence of somatic hypermutation of the immunoglobulin variable region of the heavy chain gene (IgVH), strongly associated with overexpression of ZAP-70 [10,11,12,13].