CA125, also known as glycoantigen 125, is a tumor marker, which is often found to be elevated in malignant tumors, such as ovarian epithelial cancer, fallopian tube cancer, endometrial cancer, lung cancer and gastrointestinal adenocarcinoma, etc. Therefore, when this indicator is found to be higher than normal, CT examination of the chest and abdomen should be completed to clarify whether the disease is present. However, it is only an auxiliary diagnostic index, not a confirmatory index of malignant tumor, but only used to monitor the change of malignant tumor, evaluate the effect of treatment and predict the prognosis. Elevated CA125 can also be seen in benign diseases, such as massive ascites, benign ovarian tumors, etc., and regular monitoring can assess the condition of malignant tumors.