. Author manuscript; available in PMC: 2021 Apr 1.

Published in final edited form as: Surg Oncol Clin N Am. 2020 Apr;29(2):185–208. doi: 10.1016/j.soc.2019.11.003

Table 2.

2015 WHO classification of bronchopulmonary neuroendocrine epithelial neoplasms

Classification	Mitotic Count	Necrosis	Other Features
Carcinoid tumor:
Typical carcinoid	<2 per 2 mm²	Absent	Tumor must be ≥0.5 cm
Atypical carcinoid	2–10 per 2 mm²	Present	Diagnosis based on presence of either or both features
Poorly differentiated neuroendocrine carcinoma:
Small cell carcinoma	>10 per 2 mm²	Frequent	Characteristic histology
Large cell neuroendocrine carcinoma	>10 per 2 mm²	Frequent	Organoid morphology and expression of at least 1 general neuroendocrine marker

Reprinted from Travis WD, Colby TV, Corrin B et al. (1999). Histological Typing of Lung and Pleural Tumours. WHO International Histological Classification of Tumours 3rd ed. Springer-Verlag: Berlin. With kind permission of Springer Science + Business Media.