Management of gastric and duodenal neuroendocrine tumors

Table 1 Histological grading of gastrointestinal neuroendocrine neoplasms

ENETS grading	Mitotic index (× 10 HPF)	Ki-67 proliferation index	WHO classification 2010
G1	< 2	≤ 2%	NET G1 (carcinoid)
G2	2-20	3%-20%	NET G2
G3	> 20	> 20%	NEC G3; large-cell or small-cell type

ENETS: European Neuroendocrine Tumor Society; HPF: High power field; NET: Neuroendocrine tumor; NEC: Neuroendocrine carcinoma.

Table 2 Characteristics of gastric neuroendocrine tumors

Characteristic	Type I G-NETs	Type II G-NETs	Type III G-NETs
Proportion of all G-NETs	70%-80%	5%-10%	10%-15%
Associated disease	Chronic atrophic gastritis	MEN type 1/ZES	None
Gender	Women > men	Women = men	Women < men
Tumor number	multiple	multiple	single
Tumor size	< 10 mm	< 10 mm	> 10 mm
Tumor location	fundus or corpus	fundus or corpus	Any region
Histology	Usually NET G1	NET G1/G2	Usually NEC G3
Invasion depth	Mucosa or submucosa	Mucosa or submucosa	Any depth
Serum gastrin	High	High	Normal
Gastric pH	High	Low	Normal
Risk of Metastasis	2%-5%	10%-20%	> 50%
Prognosis	Excellent	Good	Poor

G-NET: Gastric neuroendocrine tumor; MEN: Multiple endocrine neoplasia; ZES: Zollinger-Ellison syndrome.