Alpha-fetoprotein (AFP) !

AFP is the 'fetal albumin'; in adults it rises in liver cancer and germ cell tumours, and in pregnancy it flags neural tube defects.

Updated 2026-11-01

Key facts

A glycoprotein made by the yolk sac and fetal liver; in adults it almost disappears.
Marker of hepatocellular carcinoma and non-seminomatous germ cell tumours (yolk sac); pure seminoma makes no AFP.
In pregnancy, high maternal AFP: open neural tube defects, abdominal wall defects, multiple pregnancy or wrong dates; low: risk of trisomy 21 (with other markers).
It also rises in acute and chronic hepatitis and cirrhosis (liver regeneration), without cancer.
Reference values and cut-offs vary by laboratory and, in pregnancy, by gestational week.

What it measures: serum AFP concentration (in pregnancy reported as multiples of the median, MoM, for that week).
Where it comes from: fetal liver and yolk sac make it as a carrier protein; tumours with a fetal phenotype express it again.
Why it rises: hepatocellular carcinoma, hepatoblastoma, yolk sac tumour, embryonal carcinoma, liver regeneration, ataxia-telangiectasia, tyrosinaemia type 1.
Pitfalls: a third or more of small hepatocellular carcinomas do not raise it; active hepatitis can raise it without cancer; in pregnancy the gestational age must be known accurately.
A seminoma with a high AFP is managed as non-seminomatous, because it has a component that makes it.

In cirrhosis, a steadily rising AFP calls for imaging to look for hepatocellular carcinoma.
With β-hCG and LDH it stages testicular germ cell tumours.
Prenatal screening with AFP is combined with ultrasound; preconception folic acid reduces neural tube defects.

Think of the answer, then tap the question to see it.

Which fetal tissues make AFP?

The yolk sac and fetal liver; adults make almost none.

Which testicular tumour does not make AFP?

Pure seminoma; a seminoma with a high AFP is treated as having a non-seminomatous component.

What does a high second-trimester maternal AFP suggest?

An open neural tube or abdominal wall defect, a multiple pregnancy or wrong gestational dates.

Why does a normal AFP not rule out hepatocellular carcinoma?

Many such tumours, especially small ones, do not raise it; so surveillance relies on ultrasound.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Alpha Fetoprotein (AFP) Tumor Marker Test: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Alpha-Fetoprotein (AFP) Test: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Alpha fetoprotein: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.