In contrast with the lack of lymphomagenic effect of AID, alone or combined with p53 deficiency, we show here that in the absence of UNG, a mild increase in AID expression (R26+/AIDCd19+/cre mice) is sufficient to decrease mean survival and contributes to lymphoma evolution, supporting the notion that UNG can act as a tumor suppressor in the context of B cell lymphomagenesis. The gene discussed is AICDA; the disease is lymphoma.