CEACAM5 and cancer: In this study, the differences in serum carcinoembryonic antigen (CEA) and squamous cell carcinoma antigen (SCCA) levels in patients with different pathological types of malignant lung nodules were statistically significant (P < 0.05), and the serum SCCA levels in patients with SC were significantly higher than those in patients with AIS, MIA, and IAC (P < 0.05), and the CEA levels in patients with IAC were significantly higher than those in patients with AIS and MIA (P < 0.05).