ENO2 and squamous cell carcinoma: For the performance of single markers, CEA (AUC: 0.812; sensitivity: 63.9%) was the most related to lung adenocarcinoma (Figure 3(a), Table 4); CYFR21 (AUC: 0.847; sensitivity: 84.6%) and CEA (AUC: 0.804; sensitivity: 70.0%) were the best suited for squamous-cell carcinoma (Figure 3(b), Table 5); and NSE (AUC: 0.819; sensitivity: 69.0%) and CEA (AUC: 0.808; sensitivity: 60.7%) were the most related to SCLC (Figure 3(c), Table 6).