A blood test can indicate a type of cancer, according to Mayo Clinic. However, these tests are not always 100 percent accurate. Even noncancerous disorders can cause elevated levels of tumor markers.
Blood tests that can indicate cancer include the prostate-specific antigen test for prostate cancer, the calcitonin test for a type of thyroid cancer, and the cancer antigen 125 test for ovarian cancer, says Mayo Clinic. The alphafetoprotein test is used to detect liver cancer, and the human chorionic gonadotropin test is used for reproductive cancers that strike the testicles and the ovaries.
The mechanism behind these tests is that the tumors give off chemicals, called tumor markers, that circulate in the blood stream, according to Mayo Clinic.