The general principles of the new classification of neuroendocrine tumours (NET) will be applied to the entire 5th series, based on a consensus meeting in Lyon (1), dividing NEN into NET and neuroendocrine carcinomas (NEC) based on their molecular differences. Mutations in MEN1, DAXX and ATRX are entity‐defining for well‐differentiated NETs, while NECs usually have TP53 or RB1 mutations. The gene discussed is MEN1; the disease is neuroendocrine carcinoma.