Despite presenting a clear preneoplastic phenotype, Kmt2d/Crebbp dHET mice did not develop overt lymphomas even on 18 mo of follow-up (n = 0/17 vs 0/23 in littermate controls), indicating that perturbation of the epigenetic landscape alone is insufficient to drive full tumor formation and that additional genetic, epigenetic, and/or microenvironmental cues are necessary to lock these cells in a neoplastic state. The gene discussed is CREBBP; the disease is lymphoma.