Tumor Marker:- Part 8 – Alpha-Fetoprotein (AFP) updated: May 15,2023 by kamlesh kumar

Tumor Marker:- Part 8 – Alpha-Fetoprotein (AFP)

 updated: May 15,2023 by kamlesh kumar

Alpha-Fetoprotein (AFP)

Sample for Alpha-Fetoprotein (AFP)

1. The patient’s serum is needed.
2. Can take a random sample, and no fasting is needed.

Indications for Alpha-Fetoprotein (AFP)

1. For the diagnosis of liver cell carcinoma.
2. Patients with chronic active hepatitis.
3. Patients with cirrhosis and positive serology (HBV and HCV) should be tested with AFP and ultrasound abdomen.
4. AFP is a tumor marker for yolk sac tumors.
5. AFP raised in hepatoid gastric carcinoma.

Definition of Alpha-Fetoprotein (AFP)

1. The discovery of oncofetal antigen AFP and CEA was made in 1960. This was the start of tumor markers.
   1. Alpha-Fetoprotein (AFP) was found in the serum of mice with liver cell carcinoma and later in the sera of humans with liver cell carcinoma.
   2. Alpha-Fetoprotein (AFP) is a tumor marker for liver cell carcinoma and germ cell (non-seminoma) carcinoma.
2. This is a glycoprotein. This consists of a single polypeptide chain and has a 4% carbohydrate.
   1. The yolk sac produces this in small amounts and the liver with an abundant amount in the fetus.
3. It is normal after about 18 months of birth.

Alpha-Fetoprotein (AFP): AFP in fetus

Alpha-Fetoprotein (AFP): AFP in the fetus

3. It is close to albumin, genetically and structurally.
   1. The gene coding for both is chromosome 4q.
4. Its concentration is 10% of that of albumin.

Alpha-Fetoprotein (AFP) structure:

1. The fetal liver produces an alpha-1 globulin called alpha-fetoprotein. It becomes the dominant fetal serum protein in the first trimester.
   1. It reaches a peak at 12 weeks, then declines to 1% of the peak at birth.
   2. By the age of 1 year, there is a marked decrease.
2. Alpha-Fetoprotein (AFP) is a glycoprotein with a molecular weight of 70 kDa.
3. It has a single polypeptide chain and around 5% of carbohydrates.
4. Alpha-Fetoprotein (AFP) is synthesized in large quantities by the fetal yolk sac and liver during embryonic development.
5. It is the major protein in fetal circulation.
6. Alpha-Fetoprotein (AFP) is genetically and structurally identical to albumin.

The function of the Alpha-Fetoprotein (AFP)AFP:

1. AFP has increased in pregnancy, usually not >100 ng/mL.
2. Its main role is to bind and transport substances that are not water-soluble, like steroid hormones, lipids, vitamins, and bilirubin.
3. Maternal serum AFP is lower than expected in Down’s syndrome.
4. Maternal serum AFP is raised or higher level in the neural tube defect.
5. A level> 1000 µg/L indicate malignancy:
   1. At this level, 50% of liver cell carcinomas are diagnosed.
   2. It is ideal for diagnosing a liver tumor below the size of 5 cm.
   3. To find these small tumors cut-off value has to be set at a lower level between 200 to 1000 µg/L.
6. In healthy individuals is 10 µg/L.

Normal Alpha-Fetoprotein (AFP)

1. Adult = <40 ng/mL  (<40 µg/L)
2. Child <1 year = <30 ng/mL

Another source

• 0 to 15 ng/mL

Alpha-Fetoprotein (AFP) tumor marker for:

Liver cell carcinoma.

1. AFP is raised in 80% of liver cell carcinoma.
2. >500 ng/mL is diagnostic of liver cell carcinoma.
3. AFP may be raised for 18 months before the S/S appears.
4. AFP is a sensitive indicator of recurrence.
5. AFP >1000 ng/mL in 50% of the cases indicates tumor size >3 cm in diameter.

AFP in Liver cell carcinoma (Hepatoma)

6. In 90% of the cases, AFP >200 ng/mL, and 70% have a concentration of AFP >400 ng/mL.
   6. In 90% of cases of liver cell carcinoma Alpha-Fetoprotein (AFP) is raised >200 ng/mL.
   7. In 70% of the cases, liver cell carcinoma Alpha-Fetoprotein (AFP) is raised >400 ng/mL.
   8. In benign liver diseases, Alpha-Fetoprotein (AFP) rarely is >400 ng/mL.
7. This is more likely raised in immature carcinoma than the mature type of carcinoma.
8. An initial high level indicates a poor prognosis.
9. Failure to come to normal indicates a problem with surgery where there is incomplete resection or metastasis.
10. The postoperative decrease followed by an increase in the AFP indicates recurrence.
11. If there is a short doubling in the AFP value, suggest metastasis at the time of surgery.
12. AFP is useful for liver cell carcinoma:
    1. Diagnosing.
    2. Prognosis.
    3. Monitor therapy.

AFP is a tumor marker of the Germ cell tumor (nonseminomatous tumor):

1. Yolk sac tumors lead to an increase in  AFP, which correlates with the tumor prognosis; e.g., >1000 ng/mL is associated with a poor prognosis.
2. Alpha-Fetoprotein (AFP) is raised in Embryonal cell carcinoma in 27% of the cases.
3. Alpha-Fetoprotein (AFP) is raised in Malignant teratoma in 60% of the cases.
4. Alpha-Fetoprotein (AFP) is increased in Testicular teratocarcinoma in 75% of the cases.
5. Choriocarcinoma element is seen in seminoma, yolk sac, teratoma, and embryonal cell carcinoma.
6. Pancreatic carcinoma AFP is positive in 23% of the cases.
7. Gastric carcinoma AFP 18% positive.
8. Bronchogenic carcinoma is 7% positive.
9. Colon carcinoma is 5% positive.