Tumor Markers

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Tumor Markers - Cancer's Calling Cards

  • Substances (proteins, enzymes, hormones, oncofetal antigens, genetic changes) produced by tumor cells or by the body in response to cancer.
  • Ideal Characteristics:
    • High sensitivity & specificity for a single cancer.
    • Levels correlate with tumor burden & prognosis.
    • Early detection capability.
    • Cost-effective & easy to measure.
  • Classification:
    • Enzymes & Isoenzymes: PSA, LDH, ALP.
    • Hormones: HCG, Calcitonin, ADH, Gastrin.
    • Oncofetal Antigens: AFP, CEA.
    • Carbohydrate Markers: CA 125, CA 19-9, CA 15-3.
    • Proteins: Monoclonal immunoglobulins (Bence Jones proteins).
    • Genetic Markers: BRCA1/2, HER2/neu, EGFR.

⭐ AFP (Alpha-fetoprotein) is a marker for Hepatocellular Carcinoma and non-seminomatous germ cell tumors (e.g., Yolk Sac Tumor).

MarkerPrimary Association(s)Key Notes
AFPHCC, Yolk Sac Tumor↑ NTDs, pregnancy. Monitor GCT response.
β-hCGChoriocarcinoma, Mole, GCTs↑ pregnancy. Monitor GCTs, trophoblastic disease.
CA 19-9Pancreatic Ca, CholangiocarcinomaLewis Ag (-ve) no production. ↑ benign GI.
CA 125Ovarian Ca (epithelial)Monitor. ↑ endometriosis, PID, pregnancy.
CA 15-3/27.29Breast CaMonitor recurrence. Not for screening.
CEAColorectal Ca (CRC)Monitor recurrence/prognosis. ↑ other adenoCa, smokers.
PSAProstate CaScreen & monitor. ↑ BPH, prostatitis. %free PSA aids.
CalcitoninMedullary Thyroid Ca (MTC)From C-cells. MEN2. Pentagastrin test.
Chromogranin ANeuroendocrine Tumors (NETs)Carcinoid, Pheochromocytoma. General NET marker.
LDHGCTs, Lymphoma, LeukemiaNon-specific. Tumor burden, prognosis.
ThyroglobulinPapillary/Follicular Thyroid CaMonitor post-thyroidectomy. Check anti-Tg Ab.
S-100Melanoma, Schwannoma, HistiocytosisNeural crest origin.
NSESCLC, NeuroblastomaNeuroendocrine marker. Prognostic.
HER2/neuBreast Ca, Gastric CaOncogene (c-erbB2). Target: Trastuzumab.
CD20B-cell Lymphomas (most NHL)Target: Rituximab.
CD30Hodgkin Lymphoma (RS cells), ALCLReed-Sternberg cells.
BRAF V600EMelanoma, Papillary Thyroid Ca, Hairy Cell LeukemiaMutation. Target: Vemurafenib.
BCR-ABLCMLPhiladelphia t(9;22). Target: Imatinib.
ALKLung Adenocarcinoma, ALCLRearrangement. Target: Crizotinib.
ER/PRBreast CancerHormone receptors. Predicts endocrine therapy response.

Clinical Utility - Detective Work

  • Screening:
    • Limited in asymptomatic (low sensitivity/specificity).
    • Uses: PSA (prostate risk), AFP (HCC surveillance).
  • Diagnosis:
    • Aids differential; rarely definitive. Context crucial.
    • E.g., ↑ hCG/AFP strongly suggest testicular GCTs.
  • Prognosis/Staging:
    • Levels correlate with burden, stage, prognosis.
    • E.g., CA-125 (ovarian), CEA (colorectal).
  • Monitoring Therapy & Recurrence:
    • Primary value: Serial levels track efficacy; ↑ suggests recurrence.
    • ↑ levels often predate clinical/radiological signs (CEA, CA 15-3).
  • Limitations:
    • False Positives: Benign conditions (inflammation, organ failure).
    • False Negatives: Non-secreting tumors or very low levels.
    • Heterogeneous tumor expression.

⭐ Key role: Monitor therapy/recurrence, not primary screening/diagnosis.

High‑Yield Points - ⚡ Biggest Takeaways

  • AFP: ↑ in hepatocellular carcinoma, yolk sac tumors.
  • β-hCG: ↑ in choriocarcinoma, testicular germ cell tumors.
  • CA 19-9: Marker for pancreatic cancer, also cholangiocarcinoma.
  • CA-125: Monitors ovarian cancer (especially surface epithelial).
  • CEA: For colorectal cancer recurrence; also some GI, lung cancers.
  • PSA: Key for prostate cancer screening and monitoring.
  • Calcitonin: Diagnostic for medullary thyroid carcinoma.

Practice Questions: Tumor Markers

Test your understanding with these related questions

Which of the following is a tumor marker associated with ovarian solid-cystic masses?

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Flashcards: Tumor Markers

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Elevated hCG can be a paraneoplastic syndrome, such as in _____ or large cell carcinoma of lung

Hint: neuro

TAP TO REVEAL ANSWER

Elevated hCG can be a paraneoplastic syndrome, such as in _____ or large cell carcinoma of lung

pinealomas

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