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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: J Am Coll Surg. 2012 Oct 11;216(1):123–134. doi: 10.1016/j.jamcollsurg.2012.08.027

Table 1.

World Health Organization Classification of Gastrointestinal and Pancreatic Neuroendocrine Tumors

Behavior Metastasis Size, cm Muscularis propria invasion Differentiation Angio-invasion Ki-67, % Hormonal index
WHO criteria, gastrointestinal
 Benign ≤1 Well <2
 Benign/low-grade malignant 1–2 Well ± <2
 Low-grade malignant + >2 + Well + 2–20 +
 High-grade malignant + Any + Poorly + >20
WHO criteria, pancreas
 Benign ≤1 Well <2
 Benign/low-grade malignant 1–2 Well ± <2 ±
 Low-grade malignant + >4 + Well + 2–20 ±
 High-grade malignant + Any + Poorly + >20