Primary neuroendocrine tumors of the lung include typical carcinoid (low grade), atypical carcinoid (intermediate grade), and neuroendocrine carcinomas (high grade) that comprise large cell neuroendocrine carcinoma and small cell carcinoma. Pulmonary neuroendocrine tumors demonstrate histomorphologic features indicative of neuroendocrine differentiation, along with evidence of neuroendocrine differentiation as demonstrated by immunohistochemistry and/or electron microscopy. Of note, a subset of non-neuroendocrine non-small cell lung carcinomas (such as adenocarcinomas, squamous cell carcinomas, and others) can express neuroendocrine markers; however, without neuroendocrine morphology, these tumors would not be considered as neuroendocrine tumors.^1,2