Update of pathological diagnosis of pulmonary neuroendocrine tumor

Pulmonary neuroendocrine tumors are common in pathological practice and its pathological classification and histological grading are not exactly the same as that of those in the digestive tract and pancreas. In 2015 edition of World Health Organization classification, pulmonary neuroendocrine tumors are classified as carcinoid tumors (including typical carcinoid and atypical carcinoid), small cell lung carcinoma, large cell neuroendocrine carcinoma, and precursor lesion diffuse idiopathic neuroendocrine cell hyperplasia; each category has distinctive morphological and immunohistochemical features. The morphologic features including growth patterns and cytological appearances are keys for the diagnosis of neuroendocrine tumor, and immunohistochemical findings are also critical for its diagnosis. Furthermore, the diagnostic criteria vary for different types of specimen. In this article, we present a concise review and summary of the update of clinicopathological characterizations of pulmonary neuroendocrine tumor, with an emphasis on its diagnostic criteria and differential diagnosis.