CA19-9 (carbohydrate antigen 19-9 or sialylated Lewis (a) antigen) is a blood test from the tumor marker category. It was discovered in patients with colon cancer and pancreatic cancer in 1981. Increased levels of CA19-9 are also found in non-malignant conditions, such as Mirizzi's syndrome and diseases of the bile ducts and liver. The molecular weight of CA19-9 of the patients with pancreas carcinoma was ~2000kD, however those of the patients with liver disorder and diabetes mellitus were showed 2000kD and round 700kD. The assay for Pancreatic and Gastro-Intestinal Cancer marker (PC-199) measures a carbohydrate antigenic determinant expressed on a high molecular weight mucin. This mucin type of glycoprotein is found in the area of pancreatic and colon and hepatocellular carcinomas. PC 19-9 (CA 199) is also related to the Lewis blood group substances and only serum antigen from cancer patients belonging to the Le (a+b-) or Le (ab+) blood group will be CA 19-9 positive. The Pancreatic &