Table 1.

WHO classification of pancreatic endocrine tumors(Heitz et al. 2004)

1. Well differentiated endocrine tumor

1.1. Benign behavior

Confined to the pancreas, < 2 cm in diameter, ≤ 2 mitoses per 10 HPF*, ≤2% Ki-67 positive cells, no angioinvasion or perineural invasion

1.2. Uncertain behavior

Confined to the pancreas and one or more of the following features: 2 cm in diameter, > 2 mitoses per 10 HPF*, > 2% Ki-67 positive cells, angioinvasion, perineural invasion

2. Well differentiated endocrine carcinoma

Low grade malignant

Gross local invasion and/or metastases

3. Poorly differentiated carcinoma

High grade malignant

> 10 mitoses per HPF*

^*HPF: high power field