Also in this case, intrinsic and extrinsic factors may take part in the neoplastic transformation but unlike UM CLL, in M CLL the BCR might be selected by a sole antigen (autoantigen or foreign antigen) or by a group of antigens with very similar characteristics, often with evidence of a geographic-biased distribution [92,105]. Here, BCR is linked to B-cell chronic lymphocytic leukemia.