In MCL, VH CDR3 stereotypy is essentially a property of IGHV3-21 and IGHV4-34 rearrangements. Differences in the IGHV gene repertoire between clustered versus nonclustered rearrangements. As the graph clearly shows, the relative frequencies of the IGHV3-21 and IGHV4-34 genes are increased considerably among clustered rearrangements; in contrast, the IGHV1-8 gene use is significantly suppressed within this group.