. Author manuscript; available in PMC: 2015 Feb 10.

Published in final edited form as: J Thorac Oncol. 2014 Mar;9(3):414–418. doi: 10.1097/JTO.0000000000000065

TABLE 1.

WHO/IASLC Classification of Pulmonary Neuroendocrine Tumors

Grade	Nomenclature	Histopathologic Characteristics
Low	Typical carcinoid	Carcinoid morphology, less than two mitoses/10 HPFs, no necrosis, >0.5 cm diameter
Intermediate	Atypical carcinoid	Carcinoid morphology, two to 10 mitoses/10 HPFs or foci of necrosis
High	Large-cell neuroendocrine carcinoma	Neuroendocrine structure, >10 mitoses/10 HPFs, necrosis (may be extensive), cytology resembling NSCLC, IHC positive for NE markers
	Small-cell carcinoma	Small cell size, scant cytoplasm, nuclei with finely granular chromatin and faint nucleoli, >11 mitoses/10 HPFs, extensive necrosis

WHO, World Health Organization; IASLC, International Association for the Study of Lung Cancer; NSCLC, non–small-cell lung cancer; IHC, immunohistochemistry; NE, neuroendocrine; HPF, high powered fields.