BCR and B-cell chronic lymphocytic leukemia: We first applied this approach in a study of 2662 patients with CLL where we reported that CLL actually consists of two different categories, based on the BCR repertoire, with important biological and ontogenetic differences.46 The first includes cases with heterogeneous BCRs (non-clustered cases), while the second (almost 30% of cases) is characterized by a remarkably high frequency of BCR stereotypy (clustered cases).