RB1 and carcinoid tumor: Another study has highlighted that the differences between carcinoids and high-grade carcinomas (LCNEC and SCLC) reside in the prevalence rates of the most frequently mutated genes (inactivating alterations of TP53 and RB1 were enriched in carcinomas, whereas MEN1 alterations were almost exclusive to carcinoids), with the exception of SMARCA2 which results in alteration in the LCNEC only.