High frequencies of RB1/TP53 co-mutation were observed for many types of small cell carcinomas besides SCLC, such as small cell bladder cancer, small cell carcinoma of unknown primary, small cell carcinoma of the stomach, etc. However, despite the high RB1/TP53 co-mutation frequencies, due to the small sample sizes, the enrichment of RB1/TP53 co-mutation has not reached or cannot be calculated for statistical significance in some of these cancers (Figure S4). This evidence concerns the gene RB1 and urinary bladder small cell neuroendocrine carcinoma.