Univariate analysis indicated that small lung lesions, advanced pathological stage, adjuvant chemotherapy after CRC surgery, solitary pulmonary lesions with lower border irregularity, higher CEA level, and the lack of concomitant mediastinal lymph node metastasis were more likely to be associated with pulmonary metastasis than with primary lung cancer in our patient population. Here, CEACAM5 is linked to lung cancer.