Genetic lesions recurrently found in patients with newly diagnosed MCL can be grouped into several functional categories including cell cycle control (CCND1, RB1, CDK2, CDK4, CDKN2A, CDKN1B, TP53, MYC), genotoxic stress pathways (TP53, ATM, CDKN2A, MDM2), apoptosis (BCL2, MDM2, TP53, CDKN2A), key prosurvival cell signaling pathways (TRAF2, BIRC3, CARD11), and epigenetic regulation (NSD2/WHSC1, MLL2, MLL3, or SWI/SNF related, matrix associated, actin dependent regulator of chromatin SMARCA4) (Figure 1). The gene discussed is RB1; the disease is mantle cell lymphoma.