RB1 and neoplasm: These tumor types also show high frequency of RB1 gene mutations/deletions (instead of cyclin/CDK/CDKI mutations), such as small-cell lung cancer, bladder cancer, breast cancer and hepatocellular carcinoma (Ahn et al., 2014; Rubio et al., 2019; Sutherland et al., 2011; Witkiewicz & Knudsen, 2014).