Conditional knock-out alleles have been successfully employed to study the in vivo role of many lymphoma-associated tumor suppressor genes encoding for transcription factors (BLIMP1), epigenetic modifiers (EZH2, CREBBP, KMT2D, TET2), small G proteins (GNA13) and ubiquitin ligases (FBXO11). The gene discussed is TET2; the disease is lymphoma.