ATM and B-cell chronic lymphocytic leukemia: BCR IG subset 2, representing about 3% of all CLL, and known to be associated with poor prognosis22, was linked to the putative driver FAM50A. The IGHV3-21 rearrangement was also enriched for FAM50A and for ATM/del11q22, SF3B1 mutations and chr21q21.3-q22.3 gains.