HER2 Status and How It Relates to Breast Cancer

Dna helix, illustration

HER2, which is also called HER2/neu and HER-2, is the acronym for human epidermal growth factor receptor 2. Knowing your HER2 status is an important part of your diagnosis.

HER2 is a gene that codes for a protein present on the surface of cells. A healthy breast cell has two copies of the HER2 gene. In approximately 30 percent of breast cancers, breast cancer cells have more than two copies of that gene, and this leads to an over-production of the HER2 protein. As a result, the affected cells grow and divide much too quickly.

Over-expression or amplification of the HER2 gene has been shown to play a significant role in the development and progression of certain types of breast cancer and other types of cancer.

Is It Inherited?

This genetic problem is not inherited from your parents. The abnormalities of this gene are related to the cancer process.

Positive vs. Negative Test Results

If your breast cancer is tested for HER2 status, the results will be graded as positive or negative. If your results are graded as HER2 positive, that means that your HER2 genes are over-producing the HER2 protein. If your results are graded HER2 negative, then the HER2 genes are not amplified.

Available Treatments

Herceptin (trastuzumab) is a drug which is currently being used to treat HER2 positive breast cancer. It is a targeted therapy and is also referred to as an immune treatment.

This drug will be given intravenously, once every two to three weeks. Once it is in your system, Herceptin targets the HER2 proteins present in excess number on the surface of breast cancer cells. This helps to stop the growth of the HER2 positive cancer cells.

Some results of Herceptin treatment include:

  • shrinks HER2 positive tumors, before surgery
  • gets rid of HER2 positive cancer cells that have spread beyond the original tumor.
  • Helps prevent recurrence (return) of the HER2 positive cancer

Tests for HER2

Your doctor may call for a few tests:

  • FISH: Fluorescence In Situ Hybridization—this test uses fluorescent probes to look at the number of HER2 gene copies in a tumor cell. If there are more than two copies of the HER2 gene, then the cancer is HER2 positive.​
  • IHC: ImmunoHistoChemistry—this test measures the production of the HER2 protein by the tumor. The test results are ranked as 0, 1+, 2+, or 3+. If the results are 3+, your cancer is HER2-positive. If the results are 2+, you will need a FISH test to determine if the cancer is HER2-positive.

Bottom Line

HER2 positive breast cancer is diagnosed by the IHC or FISH test. A result of HER 2 positive is important, as it indicates that cancer can be treated with Herceptin, as well as Perjeta and Kadcyla. If your cancer is diagnosed as HER2 positive, it is most likely aggressive. Starting treatment as soon as possible will help improve your survival, as well as help to prevent recurrence.

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