A blood test generally refers to a tumor marker test, which can be used to generally determine or consider certain cancers, but is not 100% conclusive of the diagnosis. There are many tumor markers, such as alpha-fetoprotein (a marker for primary liver cancer), CA125 (a marker for ovarian or pancreatic cancer), CEA carcinoembryonic antigen (a marker for gastric and colorectal cancers) and so on. When the above tumor markers are abnormally high, it can only suggest the diagnosis but not confirm the diagnosis. The diagnosis of cancer must rely on the diagnosis of pathology, and the diagnosis of cancer can be confirmed when cancer cells are detected through cytology or pathology. The significance of tumor markers is important for cancer prevention and auxiliary diagnosis, as well as for prognosis of disease regression, recurrence and metastasis in the course of cancer treatment. If you have elevated tumor markers, you need to go to a regular hospital in time to judge your condition and decide the next step of treatment under the guidance of your doctor.