Blood Tests for Cancer: 13 Types & What They Show

Marcela Lemos
Clinical review: Marcela Lemos Biomedical Scientist CRBM/PE #08598
Created by: Tua Saude editing team
Key points
  • Blood tests for cancer measure tumor markers, which may be linked to certain cancers or used to monitor treatment response.
  • Abnormal tumor marker levels do not always mean cancer, as they can also increase due to infections, inflammation, or benign conditions.
  • Cancer is usually confirmed with a combination of tests, such as blood tests, imaging exams, medical evaluation, and biopsy.

Blood tests for cancer are used to measure substances in the blood called tumor markers, which may be produced by cancer cells or by the body in response to cancer. These tests, such as AFP, PSA, and CA 125, can help detect signs that may be linked to cancer and monitor how well treatment is working.

Although blood tests for cancer can provide important clues, tumor marker levels can also increase due to non-cancerous conditions, such as infections, inflammation, or benign tumors. Because of this, abnormal results need to be interpreted carefully and are usually followed by imaging tests, biopsy, or other exams.

Different blood tests evaluate specific proteins, hormones, or genetic changes linked to certain types of cancer, including breast, prostate, ovarian, and thyroid cancer. In most cases, a diagnosis is made using a combination of blood tests, imaging exams, and sometimes a biopsy to confirm the presence of cancer cells.

row of blood samples

Main tests

Some blood tests for cancer that may be ordered include:

1. AFP

What it tests: Alpha-fetoprotein (AFP) is a protein that may be measured when investigating tumors in the stomach, intestines, ovaries, or liver, as well as cancer that has spread to the liver.

Reference ranges: In general, AFP levels over 1000 ng/mL may suggest malignancy. However, AFP can also be elevated in non-cancerous conditions, such as cirrhosis or chronic hepatitis, which may cause levels around 500 ng/mL.

2. MCA

What it tests: The mucin-like carcinoma-associated antigen (MCA) test is typically used to help evaluate breast cancer.

Reference ranges: Results above 11 U/mL may suggest cancer. However, MCA levels can also be elevated in non-cancerous conditions, such as benign tumors in the ovaries, uterus, or prostate.

For breast cancer, doctors may also order CA 27.29 or CA 15-3 tests to monitor how the disease is progressing and assess response to treatment.

3. BTA

What it tests: The bladder tumor antigen (BTA) test helps detect bladder cancer. It is often used alongside other tests, such as the NMP22 and CEA tests, to improve accuracy.

Reference ranges: BTA levels are typically higher than 1 in people with bladder cancer. However, BTA can also be present in urine and may be elevated in less serious conditions, such as kidney or urethral inflammation, especially in people who use a catheter.

4. PSA

What it tests: The prostate-specific antigen (PSA) is a protein that is normally produced by the prostate, but levels can be become significantly elevated in the presence of prostate cancer. 

Reference ranges: PSA levels above 4.0 ng/mL may lead doctors to order more testing, although prostate cancer can occur with lower PSA levels. Very high PSA levels, such as levels above 50 ng/mL, may raise concern for more advanced disease.

A diagnosis cannot be made based on PSA alone and should be confirmed with further tests, such as a digital rectal exam and prostate imaging.

5. CA 125

What it tests: The cancer antigen 125 (CA 125) blood test is a tumor marker used to help evaluate ovarian cancer and monitor treatment response. This test should be ordered with other exams to support an accurate diagnosis.

Reference ranges: According to the American Cancer Society, CA 125 levels above 35 U/mL are generally considered elevated, although reference ranges can vary by lab.

CA 125 can also increase for non-cancerous reasons, including endometriosis, pelvic inflammatory disease, pregnancy, and other benign conditions.

6. Calcitonin

What it tests: Calcitonin is a hormone produced by the thyroid gland that can become elevated in people with thyroid cancer, especially medullary thyroid cancer. Calcitonin levels may also increase in some cases of breast or lung cancer.

Reference ranges: Calcitonin levels over 20 pg/mL may suggest cancer. However, abnormal results can also occur with non-cancerous conditions, such as pancreatitis, Paget’s disease, or pregnancy. 

7. Thyroglobulin

What it tests: Thyroglobulin is a protein made by the thyroid gland. This test is mainly used after thyroid cancer treatment to monitor response or check for recurrence, but it may be ordered with other tests, such as calcitonin and TSH, because thyroglobulin can be elevated even when cancer is not present.

Reference ranges: Normal thyroglobulin levels can vary by lab and by the patient’s thyroid status. High levels may suggest thyroid cancer recurrence in some cases, but they do not confirm cancer on their own.

8. CEA

What it tests: The carcinoembryonic antigen (CEA) test can help evaluate different types of cancer, especially colorectal cancer, which affects the colon or rectum.

Reference ranges: CEA levels may suggest cancer when they are 5 times higher than the normal value, which is up to 5 ng/mL in smokers and up to 3 ng/mL in non-smokers.

The doctor may also order other tumor marker tests, such as CA 19-9, CA 72-4, LDH, cathepsin D, telomerase, and HCG, as these can also show abnormal results in some types of cancer.

9. CA 15-3 marker

What it tests: The CA 15-3 marker is used to help evaluate breast cancer, determine its stage, and monitor response to treatment.

Reference ranges: CA 15-3 levels greater than 30 U/mL may be seen in breast cancer. However, levels can also increase with other cancers, such as lung, ovarian, or colorectal cancer. For this reason, CA 15-3 is usually used to monitor breast cancer rather than confirm a diagnosis.

10. CA 19-9 marker

What it tests: The CA 19-9 marker is mainly used to help evaluate pancreatic cancer. It may also be elevated in colorectal, gallbladder, or liver cancer.

Reference ranges: CA 19-9 levels greater than 37 U/mL may suggest malignancy. However, other tests and markers are needed to confirm a cancer diagnosis.

11. Protein electrophoresis

What it tests: Protein electrophoresis is one of the main tests used to help investigate and diagnose multiple myeloma. It measures immunoglobulin levels in the blood and checks for abnormal immunoglobulins.

Reference ranges: High gamma globulin levels, usually above 1.27 g/dL or greater than 18.8%, may be a sign of multiple myeloma. However, reference ranges can vary from lab to lab.

Additional tests are usually needed to confirm a multiple myeloma diagnosis, such as urine testing for M-protein, also known as Bence-Jones protein. Blood tests may also show anemia, pancytopenia, high calcium levels, or signs of kidney disease.

12. CD20 marker

What it tests: The CD20 marker test checks whether non-Hodgkin lymphoma cells have the CD20 protein. This can help the doctor decide if targeted therapy may be appropriate.

Reference ranges: Results are reported as positive (CD20+) or negative (CD20-). If the result is CD20+, treatment with monoclonal antibodies, such as rituximab, may be considered.

13. c-Kit mutation test

What it tests: The c-Kit mutation test looks for changes in the c-Kit gene. It may be performed using a blood, tumor tissue, or bone marrow sample to help evaluate cancers such as gastrointestinal stromal tumors (GIST), acute myeloid leukemia (AML), or mucosal melanoma. This test can also help guide treatment decisions.

Reference ranges: Results are usually reported as positive or negative. A positive result means a c-Kit gene mutation was found, while a negative result means no mutation was detected. Other tests, such as CD34 or P-glycoprotein, may also be needed to help confirm the diagnosis.

Genetic testing

Genetic tests for cancer can help identify DNA changes linked to cancer risk, diagnosis, prognosis, or treatment planning. These tests look for changes in cell DNA that may be linked to cancer or an increased risk of developing cancer.

Examples include liquid biopsy, gene expression testing, and whole-exome sequencing.

Confirming a diagnosis 

If cancer is suspected, the doctor may order imaging tests along with blood tests, such as:

  • Ultrasound: Checks for changes or lesions in organs like the liver, pancreas, spleen, kidneys, prostate, breasts, thyroid, uterus, and ovaries.
  • X-ray: Uses radiation to check for changes in the lungs, spine, or bones.
  • MRI: Creates detailed images to detect changes in organs and tissues, such as the breasts, blood vessels, liver, pancreas, spleen, and kidneys.
  • CT scan: May be ordered if an X-ray shows changes that need further evaluation. It can help assess areas such as the lungs, liver, spleen, pancreas, and joints.

A diagnosis is usually based on a medical assessment, blood tests, imaging exams, and biopsy. According to the National Cancer Institute, a biopsy is often the only way to know for sure whether cancer is present.

Doctors will also ask about specific cancer symptoms and evaluate them to help guide the diagnosis.

Can cancer be detected with just a CBC?

Routine blood tests, including a complete blood count (CBC), are not enough to diagnose cancer on their own. However, abnormal results combined with certain symptoms may raise suspicion and lead doctors to order further tests to confirm or rule out cancer.

Update History
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