A sharp distinction between NET and poorly differentiated neuroendocrine carcinoma (NEC) is emphasized to highlight substantial biological differences.
Pancreatic neuroendocrine neoplasms (pNENs) are rare tumors accounting for only 1%-2% of all pancreatic tumors. pNENs are pathologically heterogeneous and are categorized into three groups (neuroendocrine tumor: NET G1, NET G2; and neuroendocrine carcinoma: NEC) on the basis of the Ki-67 proliferation index and the mitotic count according to the 2010 World Health Organization (WHO) classification of gastroenteropancreatic NENs.
Clinicopathologic correlation was made among poorly differentiated neuroendocrine carcinomas (NECs/poorly differentiated histology and Ki-67 >20%) and pancreatic neuroendocrine tumours (PanNETs/Ki67 ⩽20%) and non-pancreatic neuroendocrine tumours (NP-NETs/Ki67 ⩽20%).