Table 1.
Classification of neuroendocrine neoplasms of the gastroenteropancreatic system (WHO 2017)a
| Grade | Description | Ki-67, % | Mitotic index (HPF) |
|---|---|---|---|
| G1 | well-differentiated NEN | <2 | <2/10 |
| G2 | well-differentiated NEN | 3–20 | 2–20/10 |
| G3 | well-differentiated NEN | >20 | >20/10 |
| G3b | poorly differentiated NEN or NEC | >20 | bdifferentiated into small and large cell |
a
New category: mixed NEN/non-NEN (MiNEN), hyperplastic and preneoplastic lesions.
NEN = Neuroendocrine neoplasm (also called NET = neuroendocrine tumor); NEC = neuroendocrine carcinoma; HPF = high power field.