Tumour Markers in Surgery

Tumour markers are substances (proteins, glycoproteins, hormones, enzymes, or genetic material) produced by tumour cells or by the host in response to a tumour, detectable in blood, urine, or tissue. In surgical oncology they are workhorses for monitoring and prognosis far more than for screening or definitive diagnosis. This is one of the most reliably repeated, almost-guaranteed factual topics in NEET PG surgery — the marker–malignancy pairings and their purpose are the examiner's favourite hooks.

Definition & classification

A tumour marker is a biomolecule whose presence or raised concentration correlates with the presence, burden, or behaviour of a malignancy. The ideal marker would be 100% sensitive (positive in all patients with the cancer), 100% specific (negative in everyone without it), organ-specific, and proportional to tumour load. No such ideal marker exists — this single sentence underlies most MCQ traps.

Broad classification:

• Oncofetal antigens — proteins normally expressed in foetal life, re-expressed by tumours: CEA, AFP.
• Glycoprotein / carbohydrate (CA) antigens — CA 19-9, CA 125, CA 15-3, CA 27-29.
• Hormones — beta-hCG, calcitonin, catecholamines/metanephrines, gastrin, insulin.
• Enzymes / isoenzymes — PSA (a serine protease), prostatic acid phosphatase, LDH, neuron-specific enolase (NSE), alkaline phosphatase.
• Receptors / proteins of prognostic value — ER/PR, HER2/neu (breast).
• Genetic / molecular markers — BRCA1/2, KRAS, EGFR, BRAF, microsatellite instability.

High-yield: Tumour markers are best used for MONITORING treatment response and detecting recurrence, NOT for screening the general population (low specificity gives many false positives). The one classic screening exception examiners accept is AFP + ultrasound for HCC surveillance in cirrhotics, and PSA in selected men.

The core marker–cancer table (memorise cold)

Marker	Principal malignancy	Other associations	Chief clinical use
CEA	Colorectal carcinoma	Pancreatic, gastric, breast, lung, medullary thyroid	Post-op surveillance & recurrence (NOT diagnosis/screening)
AFP	Hepatocellular carcinoma	Non-seminomatous germ cell (yolk sac), neural tube defects	Diagnosis + monitoring of HCC; staging germ cell tumours
Beta-hCG	Gestational trophoblastic disease / choriocarcinoma	Germ cell tumours (esp. choriocarcinoma component), seminoma (mild)	Diagnosis, monitoring, prognosis
CA 19-9	Pancreatic carcinoma	Cholangiocarcinoma, gastric, colorectal	Monitoring; prognosis in pancreatic cancer
CA 125	Epithelial ovarian carcinoma	Endometrial, peritoneal, fallopian tube	Monitoring response & recurrence
PSA	Prostate carcinoma	BPH, prostatitis (false +)	Detection, monitoring, recurrence
Calcitonin	Medullary thyroid carcinoma (MTC)	—	Diagnosis, screening in MEN-2 kindreds, monitoring
CA 15-3 / CA 27-29	Breast carcinoma	—	Monitoring metastatic breast cancer
Thyroglobulin	Differentiated (papillary/follicular) thyroid Ca	—	Recurrence after total thyroidectomy + RAI
Chromogranin A	Neuroendocrine tumours / carcinoid	Phaeochromocytoma	Diagnosis & monitoring of NETs
LDH	Germ cell tumours, lymphoma	Many	Prognosis, tumour bulk indicator

High-yield: CEA is the single most-tested marker — its role is follow-up after curative colorectal resection to detect recurrence (a rising CEA post-op is the earliest sign of recurrence, often before imaging). It is NOT used to screen or to make the primary diagnosis because it is also raised in smokers, IBD, cirrhosis, pancreatitis, and benign conditions.

Carcinoembryonic antigen (CEA)

An oncofetal glycoprotein of the gut mucosa. Normal < 5 ng/mL (smokers run higher, ~5–10).

• Use: Baseline pre-op level for prognosis (high CEA = worse prognosis, possible occult metastasis); serial monitoring after colorectal resection every 3 months for the first 2–3 years. A rising trend triggers a hunt for recurrence (CT, colonoscopy, PET).
• False positives: Smoking, cirrhosis, pancreatitis, peptic ulcer, IBD, hypothyroidism, benign breast disease.
• Not for screening — too non-specific.

High-yield: A persistently elevated CEA after potentially curative colorectal surgery suggests residual disease; a secondarily rising CEA suggests recurrence/metastasis (commonly hepatic).

Alpha-fetoprotein (AFP)

A foetal serum protein produced by yolk sac and foetal liver. Normal adult < 10 ng/mL.

• Hepatocellular carcinoma: AFP > 400–500 ng/mL in a cirrhotic with a liver mass is virtually diagnostic. Used with USG for surveillance in chronic HBV/HCV/cirrhosis.
• Non-seminomatous germ cell tumours (NSGCT): Raised by yolk sac (endodermal sinus) and embryonal components.
• Crucial exam point: Pure seminoma NEVER raises AFP. If AFP is elevated, the tumour is not a pure seminoma and must be treated as NSGCT regardless of histology.

Beta-hCG

Glycoprotein hormone; the beta subunit is measured.

• Markedly raised in choriocarcinoma and gestational trophoblastic disease; also in germ cell tumours containing trophoblastic (syncytiotrophoblast) elements.
• May be mildly elevated in some pure seminomas (syncytiotrophoblastic giant cells) — but a high hCG with normal AFP still keeps seminoma possible, whereas any AFP rise excludes pure seminoma.

Testicular tumour marker logic (a perennial favourite)

Tumour type	AFP	Beta-hCG	LDH
Pure seminoma	Normal (never raised)	Normal or mildly ↑	± ↑
Yolk sac tumour	↑↑	Normal	±
Choriocarcinoma	Normal	↑↑↑	±
Embryonal carcinoma	↑ or normal	↑ or normal	±
Teratoma (pure)	Usually normal	Usually normal	±

Stepwise approach to a testicular mass: Scrotal USG → serum AFP + beta-hCG + LDH (BEFORE orchidectomy) → radical inguinal orchidectomy → staging CT chest/abdomen/pelvis → markers repeated post-op to assess response.

High-yield: Markers in testicular cancer are drawn before orchidectomy (for baseline) and the surgical approach is the high inguinal route — never trans-scrotal biopsy (risk of seeding and altered lymphatic drainage). LDH reflects tumour bulk and is part of the IGCCCG prognostic staging (S category in TNM).

CA 19-9

A sialylated Lewis-a blood group antigen.

• Marker for pancreatic adenocarcinoma and cholangiocarcinoma. Used for prognosis, resectability assessment, and monitoring — not screening.
• Exam trap: Patients who are Lewis antigen-negative (~5–10% of population) cannot produce CA 19-9, giving falsely normal levels even with bulky tumour.
• Also raised in obstructive jaundice/cholangitis irrespective of malignancy — recheck after biliary decompression.

CA 125

A glycoprotein from coelomic epithelium.

• Marker for epithelial ovarian carcinoma (esp. serous). Best used to monitor response to chemotherapy and detect recurrence.
• False positives are numerous: endometriosis, PID, pregnancy, menstruation, peritonitis, ascites, cirrhosis, any peritoneal irritation. Hence poor for screening premenopausal women.
• RMI (Risk of Malignancy Index) for an adnexal mass = U × M × CA 125, where U = ultrasound score and M = menopausal status. A high RMI prompts referral to gynae-oncology.

Prostate-specific antigen (PSA)

A serine protease (kallikrein family) made by prostatic epithelium — organ-specific but not cancer-specific. Normal < 4 ng/mL.

• Raised in prostate cancer, but also in BPH, prostatitis, after DRE/instrumentation, catheterisation, ejaculation, and acute retention.
• Refinements that raise specificity: PSA density, PSA velocity, age-specific ranges, and free:total PSA ratio (a LOW free:total ratio favours malignancy).
• Used for detection, post-prostatectomy monitoring (should become undetectable), and recurrence.

High-yield: After radical prostatectomy, PSA should fall to undetectable; any detectable/rising PSA = biochemical recurrence. 5-alpha-reductase inhibitors (finasteride) roughly halve PSA — double the measured value when interpreting.

Calcitonin & medullary thyroid carcinoma

MTC arises from parafollicular C cells (neural crest origin).

• Calcitonin is the diagnostic and monitoring marker; CEA is a useful secondary marker for MTC and rising CEA with stable calcitonin suggests dedifferentiation/poor prognosis.
• MTC is a component of MEN-2A (MTC + phaeochromocytoma + parathyroid hyperplasia) and MEN-2B (MTC + phaeo + mucosal neuromas + marfanoid habitus), driven by RET proto-oncogene mutations.

High-yield: Before operating on any MTC/MEN-2 patient, exclude phaeochromocytoma first (plasma/urinary metanephrines) — operating on an undiagnosed phaeo can precipitate fatal hypertensive crisis. Prophylactic total thyroidectomy is offered to RET mutation carriers.

Diagnosis vs monitoring — the conceptual core

This distinction is the heart of every tumour-marker MCQ:

• Screening: generally NOT recommended (low specificity). Accepted exceptions: AFP + USG for HCC in high-risk cirrhotics; calcitonin in MEN-2 families; PSA in counselled men.
• Diagnosis: markers support but rarely confirm. AFP > 400 in a cirrhotic mass and very high beta-hCG in choriocarcinoma are the near-diagnostic exceptions. Tissue biopsy/histology remains the gold standard for diagnosis.
• Prognosis: higher baseline levels generally = worse outlook (CEA, LDH, CA 19-9).
• Monitoring: the dominant, evidence-backed role — track response to therapy and detect recurrence early.
• Treatment selection (predictive): HER2 → trastuzumab; ER/PR → hormonal therapy; KRAS wild-type → anti-EGFR (cetuximab) in colorectal cancer.

Complications & pitfalls of relying on markers

• False positives cause anxiety, over-investigation, and unnecessary surgery (e.g., raised CA 125 from endometriosis).
• False negatives create false reassurance (Lewis-negative patients with CA 19-9; non-secreting tumours).
• Heterophile antibodies can spuriously elevate immunoassay results (notably hCG — the "phantom hCG").
• The hook effect: extremely high antigen concentrations can paradoxically read low on some immunoassays (classic with beta-hCG, AFP) — dilute and repeat if clinically discordant.
• Marker levels fluctuate with hepatic and renal clearance; obstructive jaundice falsely raises CA 19-9.

Key differentials & "which marker?" decision aid

When an MCQ gives a clinical vignette, map symptom → organ → marker:

• Jaundice + weight loss + painless palpable gallbladder (Courvoisier) → pancreatic head Ca → CA 19-9.
• Cirrhotic with new liver mass → HCC → AFP.
• Young man, testicular lump → AFP + beta-hCG + LDH.
• Postmenopausal woman, adnexal mass + ascites → ovarian Ca → CA 125 (RMI).
• Colorectal cancer follow-up, rising trend → recurrence → CEA.
• Thyroid nodule + diarrhoea/flushing + family history → MTC → calcitonin (+CEA).
• Older man, urinary symptoms, hard nodular prostate → PSA.

Recently asked / exam angle

• "Tumour marker for medullary carcinoma thyroid" → Calcitonin (perennial single-best-answer).
• "Which marker is NOT raised in pure seminoma?" → AFP (also phrased: elevated AFP excludes pure seminoma).
• "Best use of CEA" → Monitoring recurrence after colorectal cancer resection, not screening.
• "Marker false-negative in Lewis-antigen-negative individuals" → CA 19-9.
• "RMI components" → Ultrasound score × Menopausal status × CA 125.
• "Marker for hepatocellular carcinoma" → AFP; "for choriocarcinoma" → beta-hCG.
• "Phantom hCG / heterophile antibody false positive" → measure urinary hCG to confirm (heterophile antibodies don't cross into urine).
• "PSA and finasteride" → halved; double the value.
• Image / clinical-correlation NExT-style questions increasingly pair a CT/USG with "next investigation" where the answer is the relevant serum marker for baseline/staging, then biopsy for diagnosis.

Mnemonics

• "CA 19-9 → Pancreas, CA 125 → Ovary, CA 15-3 → Breast" — fix the numbers to the organs and the rest follows.
• For testicular markers: "Seminoma → no AFP" (Seminoma starts with S, Suppresses AFP).
• MEN-2 triad: "2A = MTC + Phaeo + Parathyroid"; "2B = MTC + Phaeo + Mucosal neuromas + Marfanoid" (2B has the "Bumps" — mucosal neuromas).

Rapid revision

1. Tumour markers are mainly for monitoring and recurrence, not screening (low specificity).
2. CEA — colorectal cancer follow-up; raised in smokers and many benign conditions.
3. AFP — hepatocellular carcinoma + yolk sac germ cell tumours; never raised in pure seminoma.
4. Beta-hCG — choriocarcinoma, trophoblastic disease, germ cell tumours; can be mildly raised in seminoma.
5. CA 19-9 — pancreatic cancer; falsely normal in Lewis-antigen-negative people; raised by obstructive jaundice.
6. CA 125 — epithelial ovarian cancer; part of RMI = U × M × CA 125; many benign false positives.
7. PSA — organ-specific, not cancer-specific; finasteride halves it; undetectable after radical prostatectomy.
8. Calcitonin — medullary thyroid carcinoma; CEA is the secondary marker; linked to RET / MEN-2.
9. Always exclude phaeochromocytoma before operating in MEN-2/MTC.
10. Tissue biopsy is the diagnostic gold standard — markers support, rarely confirm.
11. LDH reflects tumour bulk and prognosis in germ cell tumours and lymphoma.
12. Draw testicular markers before radical inguinal orchidectomy; never do a trans-scrotal biopsy.