CEACAM5 and metastatic malignant neoplasm in the lymph nodes: Among the four single markers, only IL-8 and CEA have diagnostic significance in lymph node and distant metastasis of lung cancer (p < 0.05), and IL-8 was the most effective, with an AUC of 0.635 (95% CI: 0.540–0.730) for lymph node metastasis and 0.761 (95% CI: 0.674–0.848) for distant metastasis, which indicates that serum IL-8 expression exhibited good diagnostic performance in lung cancer metastasis.