Pathology and diagnosis of neuroendocrine tumors: lung neuroendocrine.

Neuroendocrine (NE) tumors of the lung include a spectrum from low-grade typical carcinoid (TC) and intermediate-grade atypical carcinoid (AC) to high-grade large cell neuroendocrine carcinoma (LCNEC) and small cell lung carcinoma (SCLC). Although NE lung tumors are frequently discussed together, as in this article, carcinoids are very different from high-grade SCLC and LCNEC. SCLC and LCNEC are found in heavy-smoking, older patients, whereas smoking is not strongly associated with carcinoid tumors. On a molecular level, SCLC and LCNEC have extensive genetic abnormalities, but there are few in TC and slightly more in AC.