SCLC usually has high expression of NSE (68.3%) or CEA (45.5%); the sensitivities of NSE and CEA in diagnosing SCLC alone are 68.3 and 45.5%, respectively, while the sensitivity of their combination increases to 81.2%; therefore, it can provide a basis for tumor screening and early diagnosis (20). The gene discussed is CEACAM5; the disease is neoplasm.