HER2-positive breast cancer is a type of breast cancer that grows and spreads quickly. The term “HER2” refers to a protein called human epidermal growth factor receptor 2, which helps control how breast cells grow. In HER2-positive cancer, the body makes too much of this protein, causing cells to grow out of control.
This type of cancer can spread (metastasize) from the breast to other parts of the body. However, the good news is that if it’s found early—before it spreads—it can often be treated successfully with targeted therapies.
How Common is HER2-Positive Breast Cancer?
In 2023, the American Cancer Society estimated that more than 290,000 women would be diagnosed with invasive breast cancer in the U.S. This includes common types like invasive ductal carcinoma and lobular breast cancer. Out of these cases, about 15% to 20% are HER2-positive. HER2-positive breast cancer is much less common in men.
Symptoms of HER2-Positive Breast Cancer
HER2-positive breast cancer often shares the same symptoms as other types of breast cancer. These symptoms may vary from person to person, but here are the most common signs to watch for:
- A lump in the breast or underarm
This is often the first noticeable sign. The lump may feel hard and painless, though not always. - Changes in breast size or shape
One breast may appear larger, swollen, or have a different shape than usual. - Nipple changes
You may notice the nipple turning inward (inverted), discharge (other than breast milk), or crusting around the nipple. - Skin changes on the breast
This could include redness, dimpling (like an orange peel), or thickening of the skin. - Pain or tenderness
Some people feel pain or discomfort in the breast or nipple area, although not everyone does. - Swelling in the lymph nodes
You may feel swollen nodes in the underarm or near the collarbone, which could be a sign the cancer has spread.
Important Note:
HER2-positive breast cancer tends to grow and spread faster than other types. That’s why early detection is important. If you notice any of these signs, talk to a healthcare provider as soon as possible.
Diagnosing HER2-Positive Breast Cancer
To determine whether a breast cancer is HER2-positive, doctors analyze a sample of the tumor tissue using one or both of the following tests:
1. Immunohistochemistry (IHC)
IHC is the most commonly used test. It involves applying a special chemical dye to the biopsy sample. This dye attaches HER2 proteins to the surface of cancer cells. Once stained, a pathologist examines the sample under a microscope and gives it a score between 0 and 3+, based on how much HER2 protein is present:
- 0 or 1+: HER2-negative
- 2+: Borderline or equivocal (may need further testing)
- 3+: HER2-positive
A score of 3+ confirms high levels of HER2 protein, meaning the cancer is HER2-positive.
2. Fluorescence In Situ Hybridization (FISH)
FISH is a more advanced and sensitive test, though it’s not as widely available as IHC. This test looks for HER2 gene amplification—meaning it checks whether there are too many copies of the HER2 gene inside the cancer cells. A fluorescent marker is used to highlight the HER2 genes, and the sample is then examined under a special fluorescent microscope. If the test shows an abnormal increase in HER2 gene copies, the cancer is considered HER2-positive.
Why These Tests Matter
Knowing your HER2 status is essential because HER2-positive breast cancers respond best to targeted therapies that specifically block the HER2 protein. Accurate testing helps your care team decide the most effective treatment plan for you.
HER2-Positive Breast Cancer: Treatment Options
If you have HER2-positive breast cancer, your doctor will recommend a treatment plan designed to target the HER2 protein and stop the cancer from growing or spreading. Your treatment will depend on the size of the tumor, the stage of the cancer, and whether it has spread to other parts of your body.
1. Surgery
Surgery is often the first step for early-stage (Stage I–III) HER2-positive breast cancer. There are two main types:
- Lumpectomy (Breast-Conserving Surgery):
Removes only the tumor and a small area of surrounding tissue. - Mastectomy:
Removes the entire breast.
2. Chemotherapy
Chemotherapy uses strong drugs to kill cancer cells. It may be given:
- Before surgery (called neoadjuvant chemo) to shrink the tumor
- After surgery (adjuvant chemo) to destroy any remaining cancer cells
- For advanced cancer that has spread beyond the breast
- Alongside targeted therapy for better results
3. Radiation Therapy
Radiation uses high-energy rays to kill cancer cells. It’s usually recommended:
- After surgery to reduce the chance of recurrence
- If the cancer has spread to other parts of the body
Types include:
- External Beam Radiation: A machine directs radiation at the cancer site.
- Brachytherapy: Small radioactive pellets are placed inside the body for a short time.
4. Targeted Therapy
Targeted therapies are designed to attack only cancer cells with HER2 overexpression, helping to protect healthy cells. These are often given with chemotherapy.
Monoclonal Antibodies
These drugs attach to the HER2 protein and block cancer cell growth:
- Trastuzumab (Herceptin): Used in early and advanced stages; often combined with chemo.
- Pertuzumab (Perjeta): Often given with trastuzumab and chemo before or after surgery.
- Trastuzumab, pertuzumab, and hyaluronidase (Phesgo): A triple combination injected under the skin.
- Margetuximab (Margenza): Used with chemo for advanced breast cancer.
Kinase Inhibitors
These oral pills block enzymes (kinases) that help cancer cells grow
Antibody-Drug Conjugates
These combine an antibody with chemotherapy. The antibody helps deliver the chemo directly to the cancer cells:
- Ado-trastuzumab emtansine: Combines trastuzumab with a chemo drug (emtansine).
- Fam-trastuzumab deruxtecan: Combines trastuzumab with another chemo (deruxtecan).
How Long Does Treatment Last?
Some targeted treatments may continue for up to a year or longer to lower the risk of recurrence. Your doctor will monitor your progress and adjust the plan as needed.
Other Types of Breast Cancer
Breast cancer isn’t just only disease. There are several types of breast cancer, each with different characteristics and treatment approaches.
Ductal Carcinoma in Situ (DCIS):
Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer where abnormal cells stay confined within the milk ducts and haven’t spread to nearby tissue.
Invasive Lobular Carcinoma (ILC):
Invasive lobular carcinoma (ILC) starts in the lobules (milk-producing glands) and can spread to nearby breast tissue and other areas.
Triple-Negative Breast Cancer:
Triple-negative breast cancer lacks estrogen, progesterone, and HER2 receptors, making it harder to treat with hormones or targeted therapies.
Metastatic Breast Cancer (Stage IV):
Metastatic breast cancer (Stage IV) means the cancer has spread beyond the breast and lymph nodes to distant parts of the body like the bones, liver, or brain.
Invasive Ductal Carcinoma (IDC):
Invasive ductal carcinoma (IDC) begins in the milk ducts and is the most common form of invasive breast cancer, capable of spreading to other tissues.
Fungating Breast Cancer:
Fungating breast cancer is a rare, advanced cancer where the tumor breaks through the skin, causing open, often painful wounds.
Metaplastic Breast Cancer:
Metaplastic breast cancer is a rare, aggressive type where cancer cells change into different cell types such as bone, muscle, or cartilage-like tissue.
Advanced Breast Cancer:
Advanced breast cancer refers to cancer that has spread locally or to distant organs, requiring more intensive treatment.
Mucinous Carcinoma:
Mucinous carcinoma is a rare breast cancer where the tumor produces mucus, which surrounds the cancer cells and often slows down its spread.
Inflammatory breast cancer (IBC):
Inflammatory breast cancer is a rare, aggressive form of breast cancer that causes redness, swelling, and warmth by blocking lymph vessels in the skin.
Life Expectancy with HER2-Positive Breast Cancer
Life expectancy with HER2-positive breast cancer depends on several factors, including:
- Tumor size
- Whether the cancer has spread
- How well the treatment works
- Hormone receptor (HR) status
Why Early Diagnosis Matters
The earlier the cancer is found, the more treatment options are available—and the better the chances of successful treatment.
Understanding 5-Year Relative Survival Rates
Doctors often use 5-year relative survival rates to estimate outcomes. These rates show how likely someone with cancer is to live for at least five years compared to someone without cancer.
Survival Rates Based on Cancer Stage and HR Status
Localized HER2-Positive Breast Cancer (has not spread):
- HR-positive: 99.3% 5-year survival rate
- HR-negative: 97.3% 5-year survival rate
Regional HER2-Positive Breast Cancer (spread to nearby lymph nodes):
- HR-positive: 90.4%
- HR-negative: 84.2%
Distant or Metastatic HER2-Positive Breast Cancer (spread to other organs):
- HR-positive: 45.8%
- HR-negative: 39.7%
While HER2-positive breast cancer can be aggressive, effective treatments—especially when started early—help many people live long, fulfilling lives. Furthermore, clinical studies for breast cancer (such as metastatic breast cancer clinical trials) explore potential new treatment options, so participating in these trials can provide access to emerging therapies and contribute to medical advancements.
Conclusion:
HER2-positive breast cancer can be aggressive, but with early detection and effective treatments, many people achieve positive outcomes. Understanding your diagnosis and exploring all available options is key. For those seeking advanced care, breast cancer clinical trials offer access to promising therapies and contribute to ongoing research and hope.
Frequently Asked Questions
Is HER2 Positive Breast Cancer Genetic?
HER2-positive breast cancer is linked to genetic changes, but it’s not usually inherited. In most cases, the HER2 gene mutation is a somatic mutation—a change that occurs during a person’s lifetime. This means it isn’t passed down from parents and doesn’t run in families.
What Causes HER2-Positive Breast Cancer?
HER2-positive breast cancer is mainly caused by a mutation in the HER2 gene, resulting in excess HER2 protein on breast cells. This triggers uncontrolled cell growth and can lead to tumor development.
Is HER2-Positive Breast Cancer a Death Sentence?
No, HER2-positive breast cancer is not a death sentence. Though once seen as more aggressive, advances in targeted treatments like trastuzumab (Herceptin) have greatly improved outcomes. With early diagnosis and proper treatment, many people live long, healthy lives.
