tumor markers
Summary
Tumor markers are biomolecules (proteins, hormones, enzymes, or antigens) produced by tumor cells or the body in response to malignancy, used to aid diagnosis, monitor treatment response, detect recurrence, and assess prognosis. They are generally not used for primary screening (except in select cases like AFP for HCC surveillance) due to limited sensitivity/specificity. High-yield examples include AFP, CEA, CA-125, CA 19-9, PSA, β-hCG, and CA 15-3.
Detail
Tumor markers are substances found in blood, urine, or tissue that are elevated in association with specific cancers, though many also rise in benign conditions, limiting their diagnostic specificity. Their primary clinical utility is in monitoring known cancer patients—tracking response to therapy and detecting recurrence—rather than initial diagnosis or population screening.
Key tumor markers for boards: - AFP (alpha-fetoprotein): hepatocellular carcinoma, yolk sac tumors (endodermal sinus tumor); also elevated in neural tube defects (used in prenatal screening) and nonseminomatous germ cell tumors. - β-hCG: choriocarcinoma, hydatidiform mole, gestational trophoblastic disease, and germ cell tumors (seminoma with syncytiotrophoblastic component). - CEA (carcinoembryonic antigen): colorectal cancer; used for recurrence monitoring, not screening; also elevated in pancreatic and gastric cancer. - CA 19-9: pancreatic adenocarcinoma. - CA-125: ovarian cancer (epithelial); also elevated in endometriosis, pregnancy, PID. - PSA (prostate-specific antigen): prostate cancer; also elevated in BPH, prostatitis; controversial for screening due to low specificity. - CA 15-3/CA 27-29: breast cancer monitoring. - Chromogranin A: neuroendocrine tumors (e.g., carcinoid). - S-100: melanoma, neural tumors (schwannoma). - Bombesin: neuroblastoma, small cell lung cancer. - LDH: nonspecific but used in germ cell tumors, lymphoma prognosis. - Alkaline phosphatase: bone metastases, Paget disease, osteosarcoma.
Clinical pearls for exams: tumor markers are rarely diagnostic alone—biopsy remains gold standard. Elevated CA-125 warrants pelvic imaging, not automatic diagnosis. AFP + β-hCG panel is classic for germ cell tumor workup. Serial CEA or CA 19-9 levels help detect recurrence post-resection. PSA screening guidelines are debated due to overdiagnosis risk.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- UWorld Step 1/Step 2 Qbank
- Goldman-Cecil Medicine
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.