CA19-9 (carbohydrate antigen 19-9, also called cancer antigen 19-91 or sialylated Lewis(a) antigen) is a tumor marker 2 that is used primarily in the management of pancreatic cancer. CA19- 9 is an antigen defined by monoclonal antibody binding to CA19-9, the tumor surface marker Sialyl-Lewis A.3. CA19-9 was discovered in the serum of patients with colon cancer and pancreatic cancer in 1981.
