RB1 and small cell lung carcinoma: The most commonly used mouse models mirror the conditional loss of Rb1 and Trp53 (referred to as the RP model, for Rb1fl/fl;Trp53fl/fl) and key histological and genome alterations found in patients (Meuwissen et al. 2003; McFadden et al. 2014), but fail to capture the high TMB that is typically observed in human SCLC.