Lung nodules do not necessarily cause elevated CEA, depending on the benign or malignant nature of the nodules. Benign lung nodules are mainly caused by infections, granulomas, etc. They are usually small in size, will not metastasize, develop slowly, and do not pose a threat to life, so they usually do not cause elevated CARC. On the other hand, malignant lung nodules mainly refer to lung cancer, which will cause certain damage to the surrounding tissues, and will metastasize and grow faster, posing a threat to life and leading to the elevation of carcinoembryonic antigen (CEA). Carcinoembryonic antigen is an important tumor marker, which mainly reflects the malignancy, metastasis and growth of the tumor. Some benign diseases, such as chronic pharyngitis, chronic laryngitis, chronic gastritis, chronic hepatitis, etc., may also cause elevated carcinoembryonic antigen. When carcinoembryonic antigen is elevated, it is recommended to go to the hospital for examination to find out the cause and timely treat the symptoms.