The most frequently mutated genes in MCL include ATM (40–50%), CCND1 (14–35%), TP53 (14–31%), mixed lineage leukemia protein 3 (MLL3, 16%), MLL2 (12–20%), tumor necrosis factor associated factor 2 (TRAF2, 7–10%), RB1 (10%), nuclear receptor binding SET domain protein 2 / Wolf-Hirschhorn syndrome candidate 1 (NSD2/WHSC1, 7–31%), baculoviral inhibitor of apoptosis (IAP) repeat containing 3 (BIRC3, 5–8%), NOTCH1 (5–14%), NOTCH2 (5%), CDKN2A (6%), and caspase recruitment domain family member 11 (CARD11). The gene discussed is RB1; the disease is mantle cell lymphoma.