MKI67 and neuroendocrine carcinoma: According to the, 2019 World Health Organization classification of gastroenteropancreatic NENs, these neoplasms are divided into three grades based on mitotic rate and Ki-67 index: Well-differentiated neuroendocrine tumors (NETs), poorly-differentiated neuroendocrine carcinomas (NECs), and mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) (29).