Thomas CF, Jett JR, Strosberg JR. Lung neuroendocrine (carcinoid) tumors: Epidemiology, risk factors, classification, histology, diagnosis, and staging. UpToDate website. https://www.uptodate.com/contents/lung-neuroendocrine-carcinoid-tumors-epidemiology-risk-factors-classification-histology-diagnosis-and-staging. Updated Feb. 26, 2018. Accessed July 9, 2018.