Table 1.
Nomenclature and classification of neuroendocrine tumors.
| Differentiation and grade | Mitotic count (/10 HPF)a | Ki-67 index (%)b | Traditional classification | ENETS/WHO classification | Moran et al. [30] |
|---|---|---|---|---|---|
| Well differentiated | |||||
| Low grade (grade 1) | <2 | ≤2 | Carcinoid, islet cell, PNET | Neuroendocrine tumor, grade 1 | Neuroendocrine carcinoma, grade 1 |
| Intermediate grade (grade 2) | 2–20 | 3–20 | Carcinoid, atypical carcinoidc, islet cell, PNET | Neuroendocrine tumor, grade 2 | Neuroendocrine carcinoma, grade 2 |
| Poorly differentiated | |||||
| High grade (grade 3) | >20 | >20 | Small-cell carcinoma | Neuroendocrine carcinoma, grade 3, small cell | Neuroendocrine carcinoma, grade 3, small cell |
| Large-cell neuroendocrine carcinoma | Neuroendocrine carcinoma, grade 3, large cell | Neuroendocrine carcinoma, grade 3, large cell |
HPF, high-power field; ENETS, European Neuroendocrine Tumor Society; PNET, pancreatic neuroendocrine tumor; aHPF = 2 mm2; at least 40 fields (at ×40 magnification) were evaluated in areas of highest mitotic density. Cutoff values were taken from American Joint Committee on Cancer staging system (seventh edition); bKi67/MIB1 antibody; percentage of 2,000 tumor cells in areas of highest nuclear labeling. Cutoff values were taken from American Joint Committee on Cancer staging system (seventh edition); cThe term atypical carcinoid only applies to intermediate grade neuroendocrine tumor of the lung.