Table A1

 WHO classification of gastroenteropancreatic endocrine tumours1,2

SiteWell differentiated
>endocrine tumour
>(Benign behaviour)
Well differentiated
>endocrine tumour
>(Uncertain behaviour)
Well differentiated
>endocrine carcinoma
>(Low grade malignant)
Poorly differentiated
>endocrine carcinoma
>(High grade malignant)
HPF, high power field.
PancreasConfined to pancreasConfined to pancreasWell to moderately differentiatedSmall cell carcinoma
<2 cm⩾2 cmGross local invasion and/or metastasesNecrosis common
<2 mitoses per 10 HPF>2 mitoses per 10 HPFMitotic rate often higher (2–10 per 10 HPF)>10 mitoses per 10 HPF
<2% Ki-67 positive cells>2% Ki-67positive cellsKi-67 index >5%>15% Ki-67 positive cells
No vascular invasionor vascular invasionProminent vascular and/or perineural invasion
StomachConfined to mucosa-submucosa,Confined to mucosa-submucosa,Well to moderately differentiatedSmall cell carcinoma
⩽1 cm. No vascular invasion>1 cm or vascular invasionInvasion to muscularis propria or beyond or metastases
Duodenum, upper jejunumConfined to mucosa-submucosa,Confined to mucosa-submucosa,Well to moderately differentiatedSmall cell carcinoma
⩽1 cm. No vascular invasion>1 cm or vascular invasionInvasion to muscularis propria or beyond or metastases
Ileum, colon, rectumConfined to mucosa-submucosa,Confined to mucosa-submucosa,Well to moderately differentiatedSmall cell carcinoma
⩽1 cm (small intestine)>1 cm (small intestine)Invasion to muscularis propria or beyond or metastases
⩽2 cm (large intestine). No vascular invasion>2 cm (large intestine) or vascular invasion
AppendixNon-functioningEnteroglucagon-producingWell to moderately differentiatedSmall cell carcinoma
Confined to appendiceal wallConfined to subserosaInvasion to mesoappendix or beyond or metastases
⩽2 cm. No vascular invasion>2 cm or vascular invasion