If you or a loved one has received a breast cancer diagnosis, you may have heard the term “HER2.” You may be wondering what it means to have HER2-positive or HER2-negative breast cancer.

Your HER2 status, along with your cancer’s hormone status, helps determine the pathology of your specific breast cancer. Your HER2 status can also help determine how aggressive the cancer is. Your doctor will use this information to evaluate your treatment options.

In recent years, there have been significant developments in the treatment of HER2-positive breast cancer. This has resulted in a better outlook for people with this type of disease.

HER2 stands for human epidermal growth factor receptor 2. HER2 proteins are found on the surface of breast cells. They’re involved in normal cell growth but can become “overexpressed.” This means that levels of the protein are higher than normal.

HER2 was discovered in the 1980s. Researchers determined that the presence of too much HER2 protein could cause cancer to grow and spread more quickly. This discovery led to research on how to slow or alter the growth of these types of cancer cells.

HER2-positive breast cancers have abnormally high levels of HER2 proteins. This can cause the cells to multiply more quickly. Excessive reproduction can result in a fast-growing breast cancer that’s more likely to spread.

Approximately 25 percent of breast cancer cases are HER2-positive.

In the last 20 years, significant progress has been made in the treatment options for HER2-positive breast cancer.

If breast cancer cells don’t have abnormal levels of HER2 proteins, then the breast cancer is considered HER2-negative. If your cancer is HER2-negative, it may still be estrogen- or progesterone-positive. Whether or not it is affects your treatment options.

Tests that can determine HER2 status include:

  • immunohistochemistry (IHC) test
  • in situ hybridization (ISH) test

There are several different IHC and ISH tests approved by the Food and Drug Administration. It’s important to test for overexpression of HER2 because the results will determine whether you’ll benefit from certain medications.

For more than 30 years, researchers have been studying HER2-positive breast cancer and ways to treat it. Targeted drugs have now changed the outlook of stage 1 to 3 breast cancers from poor to good.

The targeted drug trastuzumab (Herceptin), when used in tandem with chemotherapy, has improved the outlook of those with HER2-positive breast cancer.

A mid-1990s study first showed that this combination of treatment slowed the growth of HER2-positive breast cancer better than chemotherapy alone. For some, the use of Herceptin with chemotherapy has resulted in long-lasting remissions.

More recent studies have continued to show that treatment with Herceptin in addition to chemotherapy has improved the overall outlook for those with HER2-positive breast cancer. It’s often the primary treatment for HER2-positive breast cancer.

In some cases, pertuzumab (Perjeta) may be added in conjunction with Herceptin. This may be recommended for HER2-positive breast cancers at a higher risk of recurrence, like stage 2 and above, or for cancers that have spread to the lymph nodes.

Neratinib (Nerlynx) is another drug that may be recommended after treatment with Herceptin in cases that have a higher risk of recurrence.

For HER2-positive breast cancers that are also estrogen- and progesterone-positive, treatment with hormonal therapy may also be recommended. Other HER2-targeted therapies are available for those with more advanced or metastatic breast cancer.

If you’ve received a diagnosis of invasive breast cancer, your doctor will test for your cancer’s HER2 status. The results of the test will determine the best options for treating your cancer.

New developments in the treatment of HER2-positive breast cancer have improved the outlook for people with this condition. Research is underway for new treatments, and outlooks for people with breast cancer are continually improving.

If you receive a diagnosis of HER-positive breast cancer, learn everything you can and talk openly about your questions with your doctor.