Changes in the pathomorphological diagnosis of gastrointestinal neuroendocrine neoplasms in 2017

The following changes were introduced in 2017 WHO and TnM classifications: 1. a new group of well-differentiated neuroendocrine tumors with the proliferation index of more than 20% and mitotic count of 20 per 10 hpf (NET G3), formerly classified under neuroendocrine carcinomas (NEC G3) 2. the division of poorly differentiated neuroendocrine tumors (PD NET) with the Ki-67 index of more than 20% into two groups in terms of the degree of differentiation and prognosis: NET G3 and NEC. 3. the replacement of MANEC with MINEN within the mixed group 4. the verification of histological grading (G) criteria 5. new TNM staging criteria, based on ENETS guidelines.