There are many possible causes of lung nodules. Elevated CEA may occur in primary lung cancer or certain lung metastases, and it is uncommon clinically to see elevated CEA caused by lung nodules of other natures, such as inflammatory nodules, tuberculosis, and pulmonary nodular disease. CEA, known as carcinoembryonic antigen, is a broad-spectrum tumor marker, and its elevation can be seen in a variety of malignant tumors, such as pancreatic cancer, colorectal cancer, gastric cancer, and lung cancer. If the patient’s lung nodules are in the early stages of primary lung cancer, elevated CEA levels may occur. In addition, lung nodules formed by lung metastases from the above malignant tumors may also cause CEA elevation. In addition to lung cancer and lung metastases, various lung infections, tuberculosis, pulmonary nodular disease and other benign diseases can also form nodular lesions, which are manifested as lung nodules on imaging, while benign nodules generally do not cause CEA elevation, thus tumor markers such as CEA can be used to identify the benign and malignant nature of lung nodules. It is recommended to go to the hospital as soon as possible to clarify the nature of the nodules and then give targeted treatment.