Carcinoembryonic antigen (CEA) is a serum marker commonly used for monitoring colorectal cancer, for evaluating prognosis, postoperative surveillance, and disease advance. It is also examined in other malignancies including medullary thyroid carcinoma, breast, liver, ovarian, pancreatic, and prostate cancers. 140 Ki-67 expression is strongly related to tumor cell proliferation and is commonly used as a proliferation prognostic and predictive indicator in a number of tumor types. 141 Ki67 appeared to be closely correlated with pancreatic tumor severity. There is a correlation between Ki67 expression and patient survival in a number of other cancers, e.g. cervical and uterine cancer, non-Hodgkin's lymphoma, and gastrointestinal cancer. 141 Alpha-fetoprotein (AFP) is a glycoprotein, the expression of which is closely related to hepatocarcinogenesis, and it is a common tumor marker in a blood serum test upon screening for hepatocellular carcinoma. It is also applied in detecting other malignancies including hepatoblastoma, tumors of the ovary and testis, and gastrointestinal tract. Carbohydrate antigen 19-9 (CA19-9) is a regularly used biomarker for pancreatic ductal adenocarcinoma, a highly aggressive malignant cancer accounting for over 80% of pancreatic cancer occurrences. It is also elevated in other malignancies that include colon cancer, gastrointestinal malignancies, and cholangiocarcinoma (bile duct cancer). Carbohydrate antigen 72-4 (CA72-4) is a tumor-associated polymorphic epithelial mucin, which is highly expressed in adenocarcinomas, such as stomach, colon, breast, and lung adenocarcinomas, while it is rather low in normal tissues. It is applied as a conventional serum tumor marker for the diagnosis, monitoring, and prognosing of gastric cancer. 147