Table 1.

2017 WHO Classification of GI Neuroendocrine Tumors.

	Ki-67 index (%)	Mitotic index
Well-differentiated NENs
NET G1	<3	<2/10 HPF
NET G2	3-20	2-20/10 HPF
Poorly differentiated NENs
NEC G3	>20	>20/10 HPF
Small cell type
Large cell type
MINEN/MENEN

Source: Adapted from WHO Classification of Tumors of Endocrine Organs, Fourth edition (2017).

Abbreviations: HPF, high-power field; MINEN/MENEN, mixed endocrine non-endocrine neoplasms; NEC, neuroendocrine carcinoma; NEN, neuroendocrine neoplasm; NET, neuroendocrine tumor; WHO, World Health Organization.