Table 1.
World Health Organization (WHO) classifications of lung and gastroenteropancreatic neuroendocrine neoplasms
| Lung | Gastroenteropancreatic system | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| WHO 2015 | WHO 2010 | WHO 2019 | |||||||||
| Terminology | Mitotic index | Necrosis | Terminology | Mitotic index | Ki67 index | Terminology | Mitotic index | Ki67 index | |||
| Well‐differentiated a | TC | <2/2 mm2 | no | NET G1 | <2/10HPF | ≤2% | NET G1 | <2/2 mm2 | <3% | ||
| AC | 2‐10/2 mm2 | yes | NET G2 | 2‐20/10HPF | 3‐20% | NET G2 | 2‐20/2 mm2 | 3‐20% | |||
| NET G3 | >20/2 mm2 | >20% | |||||||||
| Poorly differentiated a | NEC | >10/2 mm2 | yes | NEC | >20/10HPF | >20% | NEC | >20/2 mm2 | >20% | ||
| Mixed neoplasms | Combined | variable | variable | MANEC | variable | variable | MiNENs | variable | variable | ||
Abbreviations: AC, atypical carcinoid; HPF, high power field; MANEC, mixed adenoneuroendocrine carcinoma; MiNEN, mixed neuroendocrine/non‐neuroendocrine neoplasm; NEC, neuroendocrine carcinoma; NET, neuroendocrine tumor; TC, typical carcinoid.
a
Morphologically well‐differentiated or poorly differentiated neoplasm.