Table 2. Pancreatic neuroendocrine tumors: WHO classification and TNM staging.

WHO 2010/ENETS grading
Grade		Differentiation	Ki-67 index (%)	Mitotic count/10 HPF
G1 (low)		Well	≤2	<2
G2 (intermediate)		Well	3–20	2–20
G3 (high)		Poorly	>20	>20
TNM staging systems for pancreatic neuroendocrine neoplasms according to AJCC and ENETS
		AJCC		ENETS
T1		Tumors limited to the pancreas, <2 cm		Tumors limited to the pancreas, <2 cm
T2		Tumor limited to the pancreas, >2 cm		Tumor limited to the pancreas, 2–4 cm
T3		Tumor extended beyond the pancreas, but not involving celiac axis or artery		Tumor extended beyond the pancreas, or invading duodenum or common bile superior mesentery artery duct
T4		Tumor involving celiac axis or superior mesentery artery		Tumor invading adjacent structures
N0		No regional lymph node metastases		No regional lymph node metastases
N1		Presence of regional lymph node metastases		Presence of regional lymph node metastases
M0		No distant metastases		No distant metastases
M1		Presence of distant metastases		Presence of distant metastases
		AJCC		ENETS
Stage	IA	T1 N0 M0	I	T1 N0 M0
	IB	T2 N0 M0	IIA	T2 N0 M0
	IIA	T3 N0 M0	IIB	T3 N0 M0
	IIB	T1–3 N1 M0	IIIA	T4 N0 M0
	III	T4 N0–1 M0	IIIB	Any T, N1 M0
	IV	Any T, Any N, M1	IV	Any T, Any N, M1

AJCC, American Joint Committee on Cancer; ENETS, European Neuroendocrine Tumor Society; HPF, high power field; TNM, tumor–node–metastasis; WHO, World Health Organization