Most cancers are diagnosed after a pathologist looks at tissue or cell samples under a microscope, according to the American Cancer Society. Biopsies of tissue samples are common during the diagnostic process and doctors order them when imaging studies or physical examination reveals a suspicious lump or mass.
Blood protein testing can detect certain types of cancers, and tumor marker tests can detect chemicals that are produced by some cancerous tumors. Tumor marker tests that look for specific antigens produced by prostate cancer are available. There are also marker tests for ovarian, medullary thyroid and liver cancers, according to Mayo Clinic.