Basic principles of a new classifi cation of neuroendocrine tumors of the gastrointestinal tract and hepatopancreatic system (WHO, 2019)
The article reviews the 2019 WHO classiﬁcation of neuroendocrine tumors of the gastrointestinal tract and hepatopancreatic system. The basic principles of the new classiﬁcation and the gradation criteria of this group of tumors are highlighted. The immunohistochemical methods for determining the histogenesis of neuroendocrine formations and their proliferative activity are described in details