HER2-Positive Breast Cancer

Medically Reviewed by Jennifer Robinson, MD on March 21, 2023
6 min read

HER2-positive breast cancer is when breast cancer cells have a protein receptor called HER2 (human epidermal growth factor receptor 2). Normally, this protein helps breast cells grow, divide, and repair themselves. But sometimes, something goes wrong in the gene that controls the HER2 protein and your body makes too many of these receptors. This causes your breast cells to grow and divide uncontrollably. About 1 of 5 breast cancers are HER2-positive.

While HER2 is more aggressive than other types of breast cancer, there are treatments that can help. You'll go over treatment options with your doctor and come up with a plan that's best for you.

A lump in your breast that feels different from the area around it is the most common symptom of breast cancer. 

Other symptoms of HER2-positive breast cancer can include:

  • Breast swelling
  • A change in its shape
  • Skin irritation or dimpling
  • Pain in the breast or nipple
  • Redness or thickness of the nipple or breast skin
  • Discharge from the nipple (not breast milk)

You may have noticed a difference in your breasts during a self-exam. Or you may have had a mammogram that showed a growth.

Doctors don't know the exact causes of breast cancer. Experts think it may be a combination of things, including your genes, environment, and lifestyle.

You can't inherit a bad copy of the HER2 gene from a parent, and you can't pass it on to your children.

If you're diagnosed with breast cancer, the doctor will check to see if yours is HER2-positive. They'll probably give you one or more of these tests:

  • The IHC test uses certain antibodies that identify the HER2 protein in a sample of breast cancer tissue.
  • The FISH test uses fluorescent pieces of DNA that stick to the HER2 gene in cells, which can then be counted under a microscope.
  • The Inform Dual ISH test uses stains that color HER2 genes in a tissue sample so they can be counted under a microscope.

Sometimes the results of a single test aren't clear. If that happens, your doctor may order another type.

  • How are you sure my cancer is HER2-positive?
  • Where exactly is my cancer?
  • What stage is it?
  • What are my treatment options?
  • What treatment do you think will work best for me?
  • How quickly do I need to start the treatment?
  • How will the treatment make me feel?
  • Is there a clinical trial I should consider?
  • Will I be able to work?
  • Do I need to have my breast removed?
  • Do I need radiation?
  • Do I need chemotherapy?
  • Do I need hormone treatment?
  • Will my insurance cover my treatment?
  • What if my cancer doesn't respond to the treatment?

Because your breast cancer is HER2-positive, your doctor will treat it a special way. This could involve:

Chemotherapy. You might get it before surgery to shrink the tumor, after surgery to kill remaining cancer cells, as treatment for cancer that has spread, or combined with other medications.

Radiation. You could get this treatment after surgery to lower the chances your cancer will return or if your cancer has spread to other body parts. There are two main types:

  • External beam radiation. A machine directs radiation to the area where the cancer was.
  • Brachytherapy. Doctors put radioactive pellets inside your body for short periods of time.

Surgery. For cancer stages I through III, your treatment will probably start with surgery. There are two main types:

  • Lumpectomy or breast-conserving surgery. The surgeon removes the tumor and some surrounding tissue.
  • Mastectomy. Your entire breast is removed.

You could also have surgery to check if the cancer has spread to nearby lymph nodes:

  • Sentinel lymph node biopsy (SLNB). The surgeon removes only the lymph node(s) under the arm to which the cancer would likely spread first.
  • Axillary lymph node dissection (ALND). The surgeon removes many (usually less than 20) lymph nodes from under the arm.

Surgery may also be an option for stage IV, or metastatic, cancer to prevent or treat symptoms or complications.

Targeted therapy. Doctors usually start HER2 treatment with special drugs called targeted therapies. They block HER2 receptors to keep cancer cells from growing. These drugs include:

You may be on this treatment plan for a long time -- up to a year. It lowers the chances that your disease will come back. If you reach that point and your cancer hasn't gotten worse, your doctor may stop the chemotherapy but keep you on the targeted treatment.

Hormone therapy. If your cancer is hormone receptor-positive, then you may also take drugs that stop the hormone estrogen from attaching to the cancer cells. There are two main types:

Clinical trial. Ask your doctor if a clinical trial is a good option for you. These are studies that test treatments not yet available to everyone to see how well they work and how safe they are. There are pros and cons. Talk to your doctor about them.

Having breast cancer can be overwhelming. Remember, though: You're in control of your treatment decisions and how you live your life.

These tips can help you stay healthy while you get treatment:

  • Get the support you need. This could be information about breast cancer, talking with someone, or help with daily tasks. It can all make a huge difference in how you feel. Listen to your body. Exercise can help you feel better, but only when you're up for it.
  • Stay nourished. If you don't have much of an appetite, eat smaller meals every few hours rather than three big meals.

About 80% of breast cancers in the U.S. are what doctors call infiltrating. This means they break through the walls of the glands or ducts where they start and grow into surrounding breast tissue. Of those cancers, around 20% are HER2-positive.

Many people do well with targeted treatments. Breast cancer of any kind is easier to treat when it's diagnosed early. But there are still ways to treat it if it spreads or comes back.

The outlook for this type of cancer depends on things like the treatment you get and the stage of your cancer. But new treatments like chemotherapy plus trastuzumab have boosted early-stage HER2 positive breast cancer survival rates:

  • 7-year disease-free: Around 93%
  • 10-year disease-free: About 70%-75%
  • Overall: 80%-85%

The American Cancer Society is a good starting place to find the support you and your family may need during treatment and after.

You may want to join a support group. That's a good way to meet people who know what you're going through because they've been through it, too.

Let your family and friends know how you're feeling. Tell them what they can do to help you. They may want to help but don't know what to do.

Also, consider talking with a counselor. That could help you handle the emotions that can come with having cancer.