Normal carcinoembryonic antigen result is a normal clinical phenomenon, or indicates that the patient’s lung tumor has been effectively controlled and the condition is stable. Carcinoembryonic antigen is a commonly used tumor indicator, but the specificity is not high, elevated indicator can be seen in lung tumors, stomach tumors, intestinal tumors, etc., and also can be seen in some inflammatory diseases, and not 100% of patients with lung tumors will be elevated, therefore, carcinoembryonic antigen can be within the normal range in some patients with lung tumors. There are also some lung tumor patients whose lung tumor lesions are effectively controlled after surgery, radiotherapy, targeted and other comprehensive treatments, so the carcinoembryonic antigen index will also remain within the normal range.