Description
CA 19-9 is the sialylated form of Lewis AntigenA. It is elevated in many types of gastrointestinal cancer, but it has been discouraged from being used as a screening test as it may be elevated in people who have no cancer. It is useful to distinguish pancreatic cancer from other diseases of the gland. In people whose red blood cells lack the Lewis antigen A, about 10% of the Caucasian population, CA 19-9 is not present on any cells, even in people with large tumors