Laboratory Tests for Breast Cancer

Breast cancer lab tests identify risk, diagnose, and guide treatment

A variety of breast cancer tests can help determine a person’s genetic risk for the disease as well as diagnose breast cancer in the early stages. Lab tests for breast cancer may also be used to:

  • Analyze characteristics of the breast cancer to determine appropriate treatment options
  • Determine whether breast cancer has metastasized (spread to other parts of body)
  • Monitor the effectiveness of breast cancer treatments and identify any recurrence of breast cancer

Lab tests for breast cancer include blood testing and biopsy.

Types of breast cancer tests

For people who are at high risk for breast cancer, such as a person who has a personal or family history of the disease, a genetic test may be recommended. The test will look for:

  • BRCA1 or BRCA2 gene mutation – A person with a mutation in either one of these genes has a significantly higher lifetime risk of developing breast cancer. This genetic test is done with a blood or saliva sample. It takes approximately one month to get the results back.

If you are getting genetic testing for breast cancer, it is important to receive genetic counseling before and after getting the results. Having a genetic tendency does not mean you will develop breast cancer in your lifetime. It’s also important to note that not all people with breast cancer have the BRCA gene mutation.

You may also get a lab test for breast cancer if you have had an abnormal mammogram, or if you or your doctor have detected something suspicious (such as a lump or hardening) in the breast.

  • Biopsy procedures – a small amount of tissue is removed (needle biopsy, surgical biopsy, or fine needle aspiration) and sent to the lab for further testing to look for signs of cancer and determine whether the sample is benign (noncancerous) or malignant (cancerous). A biopsy can also show cellular changes and behavior in cancer cells, which can help determine what kind of breast cancer treatment is best for your type of cancer. Results are usually returned within a day or two but may take slightly longer, depending on what is found during the test.

If you have been diagnosed with breast cancer, additional lab tests to identify the genes associated with cancer cell growth can further assist your medical team in providing appropriate treatment for your type of cancer.

  • HER2/neu – In some breast cancers, this gene is “over-expressed” and may respond well to breast cancer drugs that target the behavior of this gene. This is called HER2-positive breast cancer.
  • Estrogen and progesterone receptor status – Knowing whether the breast cancer cells have “receptors” for the hormones estrogen and progesterone (and the breast cancer is therefore considered “hormone dependent”) could mean that you may benefit from breast cancer hormone therapy drugs that have the ability to block or lower estrogen levels.
  • Triple negative – Breast cancers that are not hormone dependent and therefore not responsive to breast cancer hormone therapy drugs. Triple negative breast cancers tend to be fast-moving and have a less favorable prognosis (outlook), but may respond to other breast cancer treatments, such as chemotherapy.

Breast cancer lab testing can also be useful for monitoring of breast cancer treatment and to follow “tumor markers.”

  • CA 15-3, CA 27-29 – In people with breast cancer, there is usually an increase in production of certain proteins (cancer antigens or CA), which are shed by the tumor and get into the blood. These proteins can then be measured through blood testing to determine whether the breast cancer has spread or there is a recurrence of breast cancer.
  • 21-gene signature (Oncotype DX®) – This is a tumor tissue evaluation to determine risk of breast cancer recurrence.
  • 70-gene signature (Mammaprint®) – This is a tumor tissue analysis to help determine risk of breast cancer recurrence.

Your doctor may recommend additional lab tests for breast cancer as new types of tests are approved and become available.