The lifespan of Ibtk−/−Eμ-myc mice was significantly increased compared with Ibtk+/+Eμ-myc (p = 0.0004) and with Ibtk+/−Eμ-myc (p = 0.001) littermates with a median age of mortality of 150 days and 81.6% penetrance of lymphomas (Fig. 1a). This evidence concerns the gene IBTK and lymphoma.