Current status of surgical management of patients with gastroenteropancreatic neuroendocrine neoplasms

Table 1 The 2019 World Health Organization classification for gastroenteropancreatic neuroendocrine neoplasms

Morphology	Grade	Mitotic count (2 mm2)1	Ki-67 index (%)2
Well-differentiated NETs	G1	< 2	< 3
	G2	2-20	3-20
	G3	> 20	> 20
Poorly-differentiated NECs		> 20	> 20

¹Of ten high power fields = 2 mm², at least 40 fields (at × 40 magnification) evaluated in areas of highest mitotic density.

²MIB1 antibody; percentage of 500-2000 tumour cells in areas with the highest nuclear labeling.

NET: Neuroendocrine tumour; NEC: Neuroendocrine cancer.