Combining anti-PD-1 antibodies with surufatinib for gastrointestinal neuroendocrine carcinoma: Two cases report and review of literature

Table 1 Classification and grading criteria for neuroendocrine neoplasms of the gastrointestinal tract and hepatopancreatobiliary organs

Terminology	Differentiation	Grade	Mitotic rate (mitoses/2 mm2)	Ki-67 index
NET, G1	Well differentiated	Low	< 2	< 3%
NET, G2		Intermediate	2-20	3%-20%
NET, G3		High	> 20	> 20%
NEC, small-cell type (SCNEC)	Poorly differentiated	High	> 20	> 20%
NEC, large-cel type (LCNEC)			> 20	> 20%
MiNEN	Well or poorly differentiated	Variable	Variable	Variable

NET: Neuroendocrine tumor.