HER2-Positive Breast Cancer

What is HER2-positive breast cancer?

HER2-positive (HER2+) breast cancer is a fast-growing form of invasive breast cancer. If you have this kind of cancer, it means tests show high levels of a specific protein that manages how cells grow and divide That protein is human epidermal growth factor receptor 2, or HER2. This type of breast cancer is likely to spread (metastasize) from your breast to other areas of your body. Healthcare providers can successfully cure HER2-positive breast cancer if it’s diagnosed before it spreads.

How common is HER-2 positive breast cancer?

The American Cancer Society estimates that invasive breast cancers will affect more than 290,000 women and people assigned female at birth (AFAB) in 2023. (Invasive breast cancers include invasive ductal carcinoma and lobular breast cancer.) Between 15% and 20% of those breast cancer cases will be HER2-positive. Men and people assigned male (AMAB) at birth rarely develop HER2-positive breast cancer.

What are symptoms of HER2-positive breast cancer?

Like many kinds of breast cancer, this cancer subtype may not cause obvious symptoms. When it does, HER-2 positive breast cancer may cause common breast cancer symptoms:

• A change in the size, shape or contour of your breast.
• A mass or lump, which may feel as small as a pea.
• A lump or thickening in or near your breast or in your underarm that persists through your menstrual cycle.
• A change in the look or feel of your skin on your breast or nipple. Your skin may look dimpled, puckered, scaly or inflamed. Your skin may look reddish or a darker color than usual.
• A marble-like hardened area under your skin.
• A blood-stained or clear fluid discharge from your nipple.

What causes HER2-positive breast cancer?

HER2-positive breast cancer happens when the HER2 gene mutates (changes). This gene makes HER2 protein. HER2 proteins (also called receptors) are on all breast cells’ surfaces.

Normally, HER2 proteins manage breast cell growth and repair. They make sure cells divide as needed to replace damaged or dying cells.

When HER2 genes mutate, they make more copies of themselves. More HER2 genes mean more proteins. More HER2 proteins mean more breast cells divide and grow and become cancerous tumors.

What are the risk factors?

Like breast cancer symptoms, HER2-positive risk factors are the same as breast cancer. Many things may increase your risk, and you may develop breast cancer even if you don’t have the following risk factors:

• Being AFAB. Rarely, people AMAB develop breast cancer.
• Having an inherited genetic mutation like BRCA1 or BRCA2.
• Having a personal history of breast cancer.
• Having a condition like atypical ductal hyperplasia.
• Starting your menstrual cycle (period) earlier than usual.
• Starting menopause later than usual.
• Taking hormone replacement therapy.
• Having more than one drink a day of a beverage containing alcohol.
• History of radiation therapy for conditions including some types of lymphoma.

What are complications of HER2-positive breast cancer?

HER2-positive breast cancer may spread, or metastasize. About half of people with this breast cancer are diagnosed after the cancer has spread to other areas of their body, including their brains. Metastatic breast cancer to your brain can be life-threatening.

How is HER2-positive breast cancer diagnosed?

Healthcare providers diagnose all breast cancers with breast biopsies. If breast biopsies find cancer, a medical pathologist will examine breast tissue cells for signs of HER2 proteins. Laboratory tests include:

• Immunohistochemistry: Medical pathologists use immunohistochemistry tests to look for HER2 proteins in breast cancer cells. This test uses immunostaining, which gives pathologists a way to check on HER2 protein levels in cancerous cells.
• Fluorescence in situ hybridization (FISH): Pathologists may use this test to confirm IHC test results. This test finds extra copies of the HER2 gene.

If a lab test shows you have a normal number of HER2 proteins or HER2 genes, the breast cancer you have is HER2-negative. If you have high levels of HER2 proteins or HER2 genes, you have HER2-positive breast cancer.

Pathologists also break this cancer subtype into categories. To do that, they use a scoring system that’s based on the number of cancerous cells in a breast tissue sample that has high levels of HER2 protein. For example:

• If tests show low levels of the HER2 protein, the sample score is 0 or 1+. A pathologist would classify the sample as negative.
• If tests show cancerous cells and moderate levels of the protein, the sample score is 2+, and a pathologist would do FISH tests to confirm the test results.
• If tests show many cancerous cells and high protein levels, the sample score is 3+ and a pathologist would classify the sample positive.

What are treatments for HER2-positive breast cancer?

This is a form of invasive breast cancer, so treatments will vary depending on factors like cancer stages and HER2 status. Treatments may include:

• Targeted therapy, specifically monoclonal antibody therapy, tyrosine kinases inhibitor therapy and antibody-drug conjugates (ADCs). ADCs treat cancer by targeting the surfaces of cancerous cells. ADCs combine cancer drugs and antibodies that seek out cancerous cells.
• Chemotherapy to shrink tumors before providers do surgery to remove them (adjuvant or neoadjuvant therapy).

What are common treatment side effects?

Side effects may be different depending on the treatment. If you’re receiving treatment, ask your healthcare provider how treatment may affect you, including how it may affect your daily life. Also, ask your provider about palliative care. Palliative care helps manage breast cancer symptoms and treatment side effects so you’re as comfortable as possible as you go through treatment.

Can HER2-positive breast cancer be prevented?

Probably not. While there are things you can do to reduce your overall breast cancer risk, HER2-positive breast cancer happens when the HER2 gene mutates, creating cancerous cells. Researchers are still studying why that happens and can’t yet say what might prevent HER2-positive breast cancer.

However, you can reduce your risk of breast cancer by doing the following:

• Take care of your breast health. Do regular self-exams and have regular mammograms. Watch for changes in your breasts and get regular mammograms to help detect breast cancer early on, when it’s easier to treat.
• Get to and stay at a healthy weight.This is a weight that’s right for you. Ask a healthcare provider for information on setting up healthy weight management.
• Eat a healthy diet.Some studies show a diet that includes vegetables, fruit, calcium-rich dairy foods and lean protein may reduce your risk of breast cancer. Avoiding red meat and processed meat may also reduce your risk.
• Get moving.Studies show that regular physical activity lowers breast cancer risk.
• Avoid beverages containing alcohol. Research shows a link between breast cancer and alcohol. The American Medical Association recommends women and people AFAB limit alcohol to one drink a day.

Can treatment cure HER2-positive breast cancer?

When healthcare providers talk about curing cancer, they may be talking about treatment that puts cancer into remission for years at a time. (Remission means you don’t have cancer symptoms and tests don’t detect cancer.) Providers may consider someone to be cured if that person was alive five years after receiving a diagnosis of HER2-positive breast cancer.

According to data kept by the U.S. National Cancer Institute (NCI), more than 90% of people were alive five years after receiving their diagnosis. Those people may be considered cured of cancer. But HER2-positive cancer can come back (recur) and spread to other areas of your body.

What is the survival rate for HER2-positive breast cancer?

HER2-positive breast cancer survival rates may vary depending on whether the cancer is hormone receptor-positive (HR+) or hormone receptor-negative (HR-). (These are receptors on cells that can attach to hormones.) About half of all HER2-positive breast cancers have these receptors. The NCI organizes survival rates by stages: local, regional and distant.

How do I take care of myself?

Living with breast cancer can mean living with cancer symptoms, treatment and treatment side effects. It may also mean living with uncertainty. There may be days when you feel exhausted and overwhelmed by your situation. If that sounds familiar, consider the following suggestions for taking care of yourself:

• Get enough rest. Breast cancer and treatment can be exhausting. Try to remember to rest when you need to, not just when you think you have time.
• Eat well. Treatment may affect your appetite. A diet of fruit, vegetables, lean protein and healthy grains can help you stay strong during treatment.
• Manage your stress. Cancer is stressful. Exercise can help, from regular walks to exercise programs.
• Find support. You’re a breast cancer survivor, starting the day you were diagnosed. Ask your healthcare provider about cancer survivorship programs, which may help you manage some of the challenges that come with living with breast cancer.

When should I see my healthcare provider?

You’ll see your provider regularly as you go through treatment. But you should contact them anytime you notice new changes in your breasts or your body that may be signs that HER2-positive breast cancer is spreading. For example, breast cancer that’s spread to your lungs may cause symptoms like chest pain, frequent chest infections, feeling short of breath or coughing up blood.

When should I go to the emergency room?

You should go to the emergency room if your reaction to cancer treatment is stronger than you expected. For example, you should go to the emergency room if you’re severely dehydrated from constant vomiting.

What questions should I ask my healthcare?

If tests show you have HER2-positive breast cancer, you may want to ask your provider some of the following questions:

• What is my HER2 status?
• What is my hormone receptor status?
• How do HER2 and hormone receptor status affect my prognosis?
• What treatments do you recommend?
• Should I consider taking part in a clinical trial treating HER2-positive breast cancer?

A note from Cleveland Clinic

Cancer treatment breakthroughs can be rare. That’s why cancer researchers paid close attention when studies showed that mutations in HER2 genes make cells divide faster than usual. Researchers immediately looked for and later found connections between HER2 gene mutations and certain fast-growing breast cancers. From there, they developed treatments that successfully treat early-stage HER2-positive breast cancer. Now, researchers focus on finding more effective treatments to slow or stop the cancer from spreading.

Clinical trials are where breakthroughs happen. If you have metastatic HER2-positive breast cancer, ask your healthcare provider about participating in a clinical trial. They’ll be glad to work with you.