Serum levels of CEA are elevated in the blood of patients with pancreatic cancer, gastric cancer, breast cancer, lung cancer, cervical cancer, bladder cancer, lymphomas, as well as patients with nonmalignant diseases such as gastric ulcer and duodenal ulcer, colitis ulcerosa, cirrhosis and chronic pancreatitis [13,14,31,32,33,34]. Here, CEACAM5 is linked to gastric cancer.