Table 1.
Classification for gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs).
| Terminology | Differentiation | Grade | Mitotic Rate (Mitoses/2 mm2) * | Ki-67 Index % ** |
|---|---|---|---|---|
| NET, G1 | Well differentiated | Low | <2 | <3% |
| NET, G2 | Intermediate | 2–20 | 3–20% | |
| NET, G3 | High | >20 | >20% | |
| NEC, small-cell type (SCNEC) | Poorly differentiated | High | >20 | >20% |
| NEC, large-cell type (LCNEC) | >20 | >20% | ||
| MiNEN | Well or poorly differentiated | Variable | Variable | Variable |
* mitotic rates are determined by counting in 50 fields of 0.2 mm2; ** Ki-67 values are expressed as the percentage of positive cells. Abbreviations: LCNEC, large-cell neuroendocrine carcinoma; MiNEN, mixed neuroendocrine–non-neuroendocrine neoplasm; NEC, neuroendocrine carcinoma; NET, neuroendocrine tumour; SCNEC, small-cell neuroendocrine carcinoma.