The most characteristic features of this subtype are as follows: 1) usage of IGHV3-21, IGHJ6, and IGLV3-21, with a short 9 – amino acid-long HCDR3; 2) the high frequency of del(13q), del(11q), and SF3B1 mutations [24]; and 3) poor clinical outcome independent of IGHV mutational status [45] since it includes both U-CLL and M-CLL cases [46]. This evidence concerns the gene SF3B1 and B-cell chronic lymphocytic leukemia.