CA199 is a glycoproteins, a kind of tumor marker, and the corresponding indexes need to be examined by blood test, which can provide guidance basis for the auxiliary diagnosis of malignant tumors, therapeutic effect and prognosis by judging the changes of values. CA199 exists in the form of mucin in the blood, after the emergence of malignant tumors (pancreatic cancer, gastrointestinal tract tumors, etc.), because of the massive secretion of the corresponding proteins by the tumor cells, which will lead to a significant increase in its content in the serum, and the changes in the value can be detected through the blood sampling and laboratory test, which can provide the basis for diagnosis on the occurrence and development of the tumors. After the increase of corresponding indexes is detected through blood sampling, it is necessary to determine the location of the tumor and the lesion condition through imaging examination, and after the condition is determined, standardized treatment will be carried out under the guidance of clinicians.