CYFRA-21 and Pro-GRP were consistent among the better markers for NSCLC and SCLC diagnosis, respectively, as found by Visser et al. [59] and Korkmaz et al. [60], whereas Wen et al. [61] elected CEA and NSE as the most effective classifiers for SCLC. This evidence concerns the gene CEACAM5 and small cell lung carcinoma.