Table 1: WHO 2010 classification of NEN/NETs.

Grade 1Grade 2Grade 3*

Metastases+
Muscularis propria invasion±+
Tumor size (cm)≤2>2Any
Mitoses/10 HPF**<22–20>20
Ki 67 index %≤23–20>20
Angio-invasionNeverLateAlways

Grade 3 are divided into small cell and large cell neoplasms.
HPF: high-power fields.