As in the case of invasive/metastatic leukemia/lymphomas, this thymus–restricted tumorigenesis was observed, although at lower rates, in one–year–old wild type (≈17%, n = 25) and Rasgrf2–/– (≈22%, n = 20) mice (Figure 4D), further suggesting that Vav1 accentuates the intrinsic tendency of this mouse strain to develop thymic lymphomas rather than promoting tumorigenesis in an autonomous fashion. This evidence concerns the gene VAV1 and thymus lymphoma.