# Tumour Markers > Tumour markers for NEET-SS Medical Oncology: PSA as the only screening marker, AFP thresholds in HCC, marker-tumour pairs and monitoring principles. - Canonical URL: https://prepelephant.com/topics/neet-ss/medical-oncology/tumour-markers-ss - Exam / course: NEET-SS · Subject: Medical Oncology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Tumour Markers", PrepElephant, https://prepelephant.com/topics/neet-ss/medical-oncology/tumour-markers-ss ## Direct answer No tumour marker is sensitive or specific enough to diagnose a cancer on its own; their legitimate roles are risk stratification, monitoring response and detecting relapse, and PSA remains the only marker accepted for population screening, and even that contentiously. Diagnosis rests on histopathology, with two quasi-exceptions worth memorising: AFP at classically 400 ng/mL with a liver mass in a cirrhotic patient, and a choriocarcinoma-level beta-hCG, can carry enough weight to start treatment while tissue is obtained. Markers add most value when trended serially against imaging, never as isolated numbers. ## What you must remember - **PSA:** the only marker used for screening; values above 10 ng/mL raise cancer probability steeply; used with digital rectal examination and multiparametric MRI, not as a standalone biopsy trigger. - **CEA:** colorectal monitoring, not screening or diagnosis; smoking, liver disease and renal impairment falsely raise it; a preoperative value above 5 ng/mL predicts relapse risk. - **CA 19-9:** pancreatic and biliary tract monitoring; 5–10 per cent of the population are Lewis antigen-negative and cannot produce it at all — a "normal" CA 19-9 in florid pancreatic cancer is a recognised viva answer. - **CA 125:** ovarian cancer monitoring and monitoring of fallopian tube and primary peritoneal cancers; endometriosis, ascites, cirrhosis with fluid, pleural disease and pregnancy all elevate it, which is why it screens only high-risk women with ultrasound. - **AFP:** hepatocellular carcinoma (classically diagnostic above 400 ng/mL in a cirrhotic with a mass; contemporary guidance accepts lower thresholds with characteristic imaging), yolk sac tumours and hepatoblastoma; pregnancy and chronic hepatitis flares confound. - **Beta-hCG and LDH:** essential staging investigations in testicular cancer alongside AFP — beta-hCG for choriocarcinoma and seminoma, AFP for yolk sac and embryonal components; any AFP elevation in a purported seminoma means a non-seminomatous element and non-seminoma management. - **The haematology set:** serum and urine M-protein with serum free light chains for myeloma (with beta-2 microglobulin for prognosis), and inhibin for granulosa cell tumour of the ovary; thyroglobulin monitors differentiated thyroid cancer after thyroidectomy, calcitonin screens medullary carcinoma families. ## A marker panel worked through a testicular mass A 26-year-old has a right testicular swelling and a chest radiograph with normal findings. Bloods: AFP 920 ng/mL, beta-hCG 1,800 IU/L, LDH twice normal. Before any pathology arrives, the markers have already dictated the pathway: this is a non-seminomatous germ cell tumour until proven otherwise, staged as good or intermediate risk by IGCCCG criteria using the very same three markers plus metastatic sites. Orchidectomy via inguinal approach follows, and if the histology returns "pure semoma" while the AFP is elevated, the markers override the microscope — hidden yolk sac elements exist, and management is as non-seminoma. Thereafter the markers decay by their half-lives (AFP about 5–7 days, beta-hCG 24–36 hours); failure of the expected decay after orchidectomy means occult metastatic disease, and a rising marker during surveillance triggers treatment without waiting for radiology. This is the cleanest demonstration in oncology of markers as biology in real time. ## Where students slip The commonest error is promoting a marker to a diagnostic test: ordering CEA to "rule out" colon cancer in a patient with altered bowel habit, or CA 125 to screen an asymptomatic aunt — both generate false positives that cascade into invasive work-ups. The reverse error is ignoring false-negative structure: the Lewis-antigen-negative patient whose pancreatic cancer never secretes CA 19-9, or the nearly a fifth of hepatocellular carcinomas that are AFP-negative, which is exactly why surveillance in cirrhosis rests on ultrasound with or without AFP every six months rather than the blood test alone. And in an Indian viva, expect the programming counterpoint: national screening under NPCDCS uses clinical examination, VIA for cervix and oral visual examination for tobacco users — no serum marker is deployed at programme level, because none meets screening standards. ## Frequently asked questions ### Which tumour marker is acceptable for population screening? Only PSA, for prostate cancer, and even then with shared decision-making; no other marker has the operating characteristics for screening asymptomatic people. ### What AFP level traditionally clinches hepatocellular carcinoma without biopsy? A value above 400 ng/mL with a space-occupying liver lesion in a cirrhotic patient, although current guidance allows lower values with classic arterial hyperenhancement and washout on imaging. ### Why can CA 19-9 be normal in advanced pancreatic cancer? About 5–10 per cent of people are Lewis antigen-negative and biochemically cannot synthesise CA 19-9, so the tumour marker is uninformative regardless of burden. ### What does an elevated AFP in apparent seminoma signify? A non-seminomatous component — yolk sac elements — and the patient must be managed as non-seminomatous germ cell tumour regardless of the reported histology. ### How are beta-hCG and LDH used beyond diagnosis in germ cell tumours? As IGCCCG prognostic staging variables and serial monitors: post-orchidectomy failure to decay by half-life, or later rise, defines persistent disease and drives treatment ahead of imaging. ### Which markers form the myeloma response panel? Serum M-protein, urine Bence Jones protein, serum free light chains and beta-2 microglobulin, measured serially to define haematological response.