The combination of serum CYFRA21-1 and PE CEA showed the best diagnostic value in distinguishing cytology-negative MPE from BPE with an AUC of 0.834 (0.808–0.858), higher sensitivity (67.7%), specificity (91.0%), PPV (61.5%), and PLR (9.55) than a single tumor marker (Figure 2; Table 5). The gene discussed is CEACAM5; the disease is neoplasm.