Carcinoembryonic antigen, as a tumor marker, does not have an upper limit of maximum value. In some testing methods used by some testing facilities, the maximum value that may be measured is 1000ng/ml or 500ng/ml. If the value is greater than this, it will not be displayed in detail, but only greater than 1000ng/ml. However, there is no upper limit to the maximum value of carcinoembryonic antigen, and the higher the indicator of carcinoembryonic antigen, the more serious the progression of malignant tumor may be. Carcinoembryonic antigen indexes are more frequently elevated in colon malignancy and lung malignancy, but the value of the index alone cannot determine whether it is a malignant tumor, such as suspected colon cancer must rely on colonoscopy for pathology to confirm the diagnosis.