MKI67 and neuroendocrine neoplasm: Ki67 index/mitotic count into well differentiated neuroendocrine tumours (NET) with a Ki67 index ≤20% (including G1/G2 GEP-NET and typical/atypical carcinoid of lung); and undifferentiated, highly proliferative tumours with a Ki67 > 20% termed as neuroendocrine carcinomas (NEC; see Table 1; [2]).