Studies have shown that the blood levels of tumor markers are significantly higher in patients with malignant tumors than in healthy individuals [43].CEA is a glycoprotein located on the cell surface and is synthesized in early fetal life by the gastrointestinal tract, liver, and pancreas, and in adults, the epithelial tissue of the gastrointestinal tract and the liver and pancreas can also synthesize small amounts of CEA and secrete it into the digestive tract at low levels under normal conditions [44]. Here, CEACAM5 is linked to cancer.