Clin Cancer Res 24 (5): 1038 - 1047, 2018. doi: 10.1158/1078 - 0432.CCR-17 - 2289 Classification of Lung Carcinoma Lung cancer is classified into 2 major categories: Small cell lung cancer (SCLC), about 15% of cases Non-small cell lung cancer (NSCLC), about 85% of cases SCLC is highly aggressive and almost always occurs in people who smoke.