A substance whose presence in blood serves as a biochemical indicator for the possible presence of a malignancy. Examples of markers and the malignancies they may indicate are carcinoembryonic antigen for cancers of the colon, lung, breast, and ovary; beta subunit of chorionic gonadotropin for trophoblastic and testicular tumors; alpha-fetoprotein for testicular teratocarcinoma and primary hepatocellular carcinoma; and prostate-specific antigen for prostate cancer.
A protein present in blood, urine, or body tissues that can be quantified and employed for the identification of cancerous presence.