Carcinoembryonic antigen, also known as CEA, is an indicator that cannot exclude the possibility of cancer if it is very low, but also of cancer in other areas. CEA may be elevated in colon or lung malignancies, but in other malignancies, such as bone malignancies or gynecological malignancies, this index may be normal or low. To determine whether it is a malignant tumor, in addition to tumor marker test results, it is necessary to combine with imaging examinations, including CT, MRI, or gastroscopy or colonoscopy to find lesions and further pathological examinations to confirm the diagnosis. Carcinoembryonic antigen can be used as an evaluation of whether the tumor is recurring after surgery, and can also be used as tumor screening, but it cannot confirm whether it is cancer.