HER2-Positive Breast Cancer

Medically Reviewed by Shruthi N, MD on September 12, 2024
Written by Stephanie Watson
10 min read

HER2-positive breast cancer is when breast cancer cells have a protein receptor called human epidermal growth factor receptor 2 (HER2). 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 15%-20% of breast cancers are HER2-positive.

While HER2 is more aggressive than other types of breast cancer, there are treatments that can help. You can 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)

If you've noticed a difference in your breasts during a self-exam or if a mammogram has shown a growth, see a doctor.

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

Some common risk factors for HER2-positive breast cancer are:

  • Being female or assigned female at birth
  • Having overweight or obesity
  • Having dense breasts
  • Drinking alcohol more than moderately
  • Early onset of period
  • Late onset of menopause
  • Having had breast cancer before
  • Having previous radiation to the chest for a condition such as lymphoma
  • Using some types of hormone replacement therapy (HRT) or birth control pills

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 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. This test offers results faster than the FISH HER2 test. Labs can get results from the Dual ISH test overnight, while the FISH test can take several days.

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

It can be hard to remember all the questions you’d like to ask the doctor during an appointment. Here are some to start with. You can also make a list of your own questions and take them with you. 

  • Where exactly is my cancer?
  • How are you sure my cancer is HER2-positive?
  • 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 breasts 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 in a special way. Depending on the size of your cancer and whether it has spread, treatment could involve:

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

  • Lumpectomy or breast-conserving surgery, in which your surgeon removes the tumor and some surrounding tissue
  • Mastectomy, in which 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) removes only the lymph node(s) under the arm to which the cancer would likely spread first.
  • Axillary lymph node dissection (ALND) removes more 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.

Chemotherapy. You might get it:

  • Before surgery to shrink the tumor
  • After surgery to kill any remaining cancer cells
  • To treat cancer that has spread
  • In combination 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 areas of your body. There are two main types:

  • External beam radiation, in which a machine directs radiation to the area where the cancer was
  • Brachytherapy, in which your doctor puts radioactive pellets inside your body for short periods

Targeted therapy. This includes drugs that specifically work to kill or stop the growth of cancer-causing cells without damaging healthy cells. They are often used together with other types of treatment.

Monoclonal antibodies are drugs that attach to HER2 receptors and block them. This helps stop the growth of cancer cells. These drugs include:

  • Margetuximab​​​​​​​ (Margenza). This monoclonal antibody drug is sometimes given with chemotherapy to treat advanced breast cancer.
  • Pertuzumab (Perjeta). This monoclonal antibody comes as an IV into a vein. Perjeta may be combined with trastuzumab and chemo, either before or after surgery to treat early-stage breast cancer, or to treat advanced breast cancer. 
  • Trastuzumab (Herceptin). This is a treatment for early- and late-stage HER2-positive breast cancer. Often, it’s given together with chemotherapy. 
  • Trastuzumab and hyaluronidase (Herceptin Hylecta). This form of trastuzumab is given as an injection under the skin.
  • Trastuzumab, pertuzumab, and hyaluronidase injection (Phesgo). This is a combination of three drugs you get as a shot under your skin.

Kinase inhibitors block a protein called kinase that causes uncontrolled cancer cell growth. They come as a pill that you take every day. Kinase inhibitors include:

Antibody-drug conjugates are two medicines in one: A monoclonal antibody combined with chemo. The antibody finds the cancer cells and delivers the chemo directly to them. Examples of these drugs are:

You may be on this treatment for a long time -- up to a year. Staying on medication lowers the chance that your disease will come back.

Hormone therapy. If your cancer is also hormone receptor-positive, meaning that it needs the hormone estrogen to grow, then you may also take drugs that lower this hormone or block its effects on cancer cells. There are two main types of hormone therapy:

Drugs that block or damage estrogen receptors:

Drugs that lower estrogen levels (aromatase inhibitors, or AIs):

Taking hormone therapy after surgery helps reduce the risk of your cancer coming back. Usually, you’ll stay on hormone therapy for at least 5 years.

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

HER2-positive breast cancer can spread to other parts of the body. Metastatic breast cancer is the term for cancer that has spread. The HER2-positive type of breast cancer is aggressive, and it spreads faster than other breast cancer types.

Most often, HER2-positive breast cancer spreads to the:

  • Bones
  • Brain
  • Liver
  • Lungs
  • Skin

Metastatic breast cancer can cause complications such as bone fractures, trouble breathing, and seizures. Depending on where the cancer spreads, it could be life-threatening. Following the treatment plan your doctor recommends can reduce your risk for complications. Even so, let your doctor know if you have symptoms such as shortness of breath, bone pain, or headaches.

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:

Be as active as possible. While you might feel too tired to complete your usual jog or Pilates session, do what you can. Even a slow walk in the fresh air can give you more energy, boost your mood, and help you sleep better. Slowly work up to at least 150 minutes of aerobic exercise and 2 days of strength training a week.

Eat to nourish your body. Chemo and other treatments can sap your strength. Replenish nutrients by eating lots of fruits and vegetables, fish, nuts, eggs, whole grains, and lean meats.

Rest as much as you can. No matter how tired you feel, the stress of having cancer and the side effects from your treatment could keep you awake at night. To help you get more rest, try to stay on a regular sleep schedule. Avoid things that might keep you from sleep, including caffeine and electronics (phone, computer, TV) before bedtime.

Control stress. Life with cancer is undoubtedly stressful. Do what you can to combat stress. Practice meditation, yoga, or deep breathing. Listen to music. Take a walk outside. Talk to a counselor or therapist. 

Get the support you need. This could involve learning about breast cancer, talking with someone, or getting help with daily tasks. The right support can make a huge difference in how you feel. 

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 are going through or have gone through the same experience.

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 not know what to do. Also, consider talking with a counselor. That could help you handle the emotions that can come with having cancer.

Bring joy back into your life. Breast cancer treatment can be a challenging period in your life, but you can still experience happiness. Take time to do the things you love, whether that’s going out to dinner with friends, watching a funny movie, or reading your favorite book.

HER2-positive breast cancer is aggressive and it spreads faster than other breast cancer types. But new targeted therapies have made HER2-positive breast cancer easier to treat and survive.

Medications can reduce the chance of the cancer returning after treatment. And even if the cancer does come back, there are ways to manage it. 

Around 90% of people who are diagnosed with HER2-positive breast cancer are still alive 5 years after diagnosis. The specific outlook for this type of cancer depends on what treatment you get, the stage of your cancer, and whether it has receptors for the hormone estrogen.

The 5-year survival for a HER2-positive, hormone receptor-positive breast cancer is:

  • Localized (cancer is only in the breast): 99%
  • Regional (cancer has spread to lymph nodes or other structures near the breast): 90%
  • Distant (cancer has spread to distant lymph nodes or organs): 46%

The 5-year survival for a HER2-positive, hormone receptor-negative breast cancer is:

  • Localized: 97%
  • Regional: 84%
  • Distant: 40%

These numbers are based on large groups of people with HER2-positive breast cancer. They don’t necessarily reflect what will happen to you. Your doctor can give you a better idea of your outlook.

You can’t always prevent breast cancer, but some risk factors are under your control. These lifestyle changes might lower your odds of getting HER2-positive breast cancer:

  • Do aerobic exercises on most days of the week.
  • Eat a nutrient-rich diet that’s high in fruits and vegetables and low in red meat and processed meats.
  • Quit smoking.
  • Get down to a healthy weight if you are overweight or you have obesity.
  • Avoid or limit alcohol.

HER2-positive breast cancers have a protein that helps them grow. This type of breast cancer tends to be more aggressive and spreads faster than other types. But thanks to monoclonal antibodies and other new targeted therapies, people are surviving longer with this cancer.

How serious is HER2-positive breast cancer?

HER2-positive breast cancer is an aggressive and fast-growing form, but it is very treatable.

What is the life expectancy of a HER2-positive breast cancer patient?

Life expectancy varies based on the cancer stage. On average, 90% of people with HER2-positive breast cancer are still alive 5 years after their diagnosis.

Is it better to be HER2-positive or negative?

HER2-positive breast cancers tend to grow and spread faster than HER2-negative ones, but they also respond better to treatment.

What is the long-term treatment for HER2-positive breast cancer?

Treatment with targeted therapies, such as monoclonal antibodies plus chemo, may continue for a year. The goal of long-term treatment is to prevent the cancer from coming back.

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