HER2-Negative Breast Cancer

HER2-negative breast cancer means the cancer cells do not have high levels of a protein called human epidermal growth factor receptor 2 (HER2). This protein helps cancer cells grow, but its absence means these cancers won't respond to specific HER2-targeted treatments. Treatment instead focuses on other characteristics of the cancer.

What is HER2-Negative Breast Cancer?

HER2-negative breast cancer occurs when cancer cells do not produce an excess amount of a protein called human epidermal growth factor receptor 2 (HER2). This protein, found on breast cells, helps control their growth. When HER2 levels are not elevated, the cancer is considered HER2-negative, meaning it will not respond to medicines specifically designed to block the HER2 protein.

The HER2 protein acts like a receiver on the surface of breast cells, signaling them to grow, divide, and repair themselves [Source 2]. In some breast cancers, the gene that makes HER2 creates too many copies, leading to an overabundance of HER2 proteins on the cell surface. This is known as HER2-positive breast cancer [Source 2]. However, about 70% to 80% of all breast cancers are HER2-negative [Source 1, Source 2]. This means the cancer cells do not have an excess of the HER2 protein. Because these cancer cells do not rely on HER2 for their growth, treatments that specifically target the HER2 protein are not effective for HER2-negative breast cancer [Source 1, Source 3]. Understanding a cancer's HER2 status is crucial for guiding treatment decisions. For HER2-negative cancers, doctors will look at other features of the cancer, such as whether it has hormone receptors (estrogen receptor (ER) and progesterone receptor (PR)), to determine the best course of action [Source 1, Source 2].

Symptoms

HER2-negative breast cancer does not have unique symptoms that distinguish it from other types of breast cancer. The signs are generally the same for any breast cancer, including a new lump or mass in the breast, changes in breast size or shape, or alterations to the skin or nipple.

The most common symptom of breast cancer, regardless of its HER2 status, is a new lump or mass in the breast or armpit [Source 1, Source 2]. This lump might feel firm or thick and could be painless, though some people experience tenderness or pain. It is important to have any new or unusual lump checked by a doctor. Other potential symptoms include changes in the size or shape of the breast, such as swelling or a noticeable difference between the two breasts [Source 2]. You might also notice skin changes, like dimpling (which can look like an orange peel), redness, scaling, or thickening of the breast skin [Source 1, Source 2]. Nipple changes, such as an inverted nipple, discharge other than breast milk, or scaling around the nipple, can also be signs [Source 1, Source 2].

Causes & risk factors

The causes and risk factors for HER2-negative breast cancer are similar to those for other types of breast cancer, as there are no specific factors unique to its HER2 status. These can include a combination of genetic predispositions, lifestyle choices, and environmental exposures, though often the exact cause for an individual remains unknown.

Breast cancer, including the HER2-negative type, often develops due to a complex interplay of various factors. While the exact cause is not always clear, several risk factors are known to increase a person's chance of developing breast cancer. These include increasing age, a family history of breast cancer, and certain genetic mutations, such as those in the BRCA1 and BRCA2 genes [Source 2]. Lifestyle choices can also play a role. These include consuming alcohol, being overweight or obese, and not getting enough physical activity [Source 2]. Hormonal factors, such as early menstruation, late menopause, or hormone therapy after menopause, can also influence risk [Source 2]. It is important to remember that having one or more risk factors does not mean you will definitely get breast cancer, and many people with breast cancer have no known risk factors.

How it's diagnosed

Diagnosing HER2-negative breast cancer typically begins with a physical exam and imaging tests like a mammogram. The definitive diagnosis, including the HER2 status, is determined through a biopsy. During a biopsy, a small tissue sample is removed from the suspicious area and examined in a lab to identify cancer cells and test for specific proteins.

If a doctor suspects breast cancer based on a physical exam or screening mammogram, further imaging tests may be ordered, such as an ultrasound or magnetic resonance imaging (MRI) [Source 1, Source 2]. These tests help to get a clearer picture of the suspicious area and determine its size and location. The only way to confirm a breast cancer diagnosis and determine its specific characteristics, including HER2 status, is through a biopsy [Source 1, Source 2]. During a biopsy, a small sample of the suspicious breast tissue is removed, usually with a needle (core needle biopsy), and sent to a pathology lab. Pathologists examine the cells under a microscope to confirm cancer and perform special tests. These lab tests determine if the cancer cells have an excess of the HER2 protein. If the levels are not elevated, the cancer is classified as HER2-negative [Source 1, Source 2]. The biopsy also checks for the presence of hormone receptors, specifically estrogen receptor (ER) and progesterone receptor (PR). This information is vital because it helps doctors choose the most effective treatments [Source 1, Source 2]. For example, if a HER2-negative cancer is also negative for ER and PR, it is called triple-negative breast cancer (TNBC) [Source 1, Source 2].

Treatment options

Treatment for HER2-negative breast cancer is tailored to the individual and depends on factors like the cancer's stage, grade, and hormone receptor status. Since these cancers do not respond to HER2-targeted therapies, common approaches include surgery, radiation therapy, and chemotherapy. Hormone therapy may also be used if the cancer is hormone receptor-positive.

The primary treatments for HER2-negative breast cancer often involve local and systemic therapies. Local treatments, such as surgery, aim to remove the tumor. This can be a lumpectomy, which removes only the tumor and a small margin of healthy tissue, or a mastectomy, which removes the entire breast [Source 2]. Radiation therapy, which uses high-energy rays to kill cancer cells, may follow surgery to reduce the risk of the cancer returning in the breast area [Source 2]. Systemic treatments, which affect the whole body, are also crucial. Chemotherapy, using powerful drugs to kill cancer cells, is a common systemic treatment for HER2-negative breast cancer, especially for more aggressive types or those that have spread [Source 1, Source 3]. If the HER2-negative cancer also tests positive for estrogen receptors (ER) or progesterone receptors (PR), hormone therapy may be prescribed. These medicines work by blocking hormones that fuel cancer cell growth [Source 1, Source 2]. For a specific subtype of HER2-negative breast cancer known as triple-negative breast cancer (TNBC), which lacks HER2, ER, and PR, treatment options can be more challenging [Source 1, Source 2]. However, newer treatments like immunotherapy, which helps the body's immune system fight cancer, and PARP inhibitors, a type of targeted therapy, are sometimes used for certain TNBC cases [Source 1, Source 3]. Your medical team will discuss the most appropriate treatment plan based on your specific cancer characteristics.

Recovery & outlook

The recovery and outlook for HER2-negative breast cancer vary widely, depending on factors such as the cancer's stage at diagnosis, its grade, and whether it is hormone receptor-positive or triple-negative. Many people achieve successful treatment outcomes, but ongoing follow-up care is essential to monitor for recurrence and manage any long-term effects.

The prognosis, or outlook, for individuals with HER2-negative breast cancer is highly individualized. Generally, HER2-negative cancers that are also hormone receptor-positive tend to have a better prognosis than triple-negative breast cancers (TNBC) [Source 1, Source 2]. This is because hormone receptor-positive cancers have additional treatment options, such as hormone therapy, which can significantly reduce the risk of recurrence. Triple-negative breast cancer, a subtype of HER2-negative, is often considered more aggressive, tends to grow and spread faster, and has a higher chance of recurrence, especially in the first few years after treatment [Source 1, Source 2]. However, advancements in chemotherapy and the introduction of new therapies like immunotherapy are improving outcomes for people with TNBC [Source 3]. After treatment, regular follow-up appointments, including physical exams and imaging, are essential to monitor for any signs of recurrence or new cancers [Source 2]. Recovery also involves managing potential side effects from treatment and focusing on overall well-being. Support groups and counseling can be valuable resources for emotional and psychological support during and after treatment.

When to see a doctor

You should see a doctor promptly if you notice any new or unusual changes in your breasts. This includes finding a new lump, experiencing changes in breast size or shape, or observing skin changes like dimpling, redness, or nipple discharge. Early detection of breast cancer, regardless of its type, significantly improves treatment outcomes.

It is crucial to be aware of your breasts and report any concerns to your healthcare provider without delay. While many breast changes are not cancerous, only a doctor can properly evaluate them. Do not wait for pain to appear, as many breast cancers are painless in their early stages [Source 2]. Specific signs that warrant a doctor's visit include: * A new lump or thickening in your breast or armpit that feels different from the surrounding tissue [Source 1, Source 2]. * Any change in the size, shape, or appearance of your breast [Source 2]. * Changes to the skin over your breast, such as dimpling, puckering, redness, or scaling [Source 1, Source 2]. * A newly inverted nipple or changes in the appearance of the nipple or the surrounding skin [Source 1, Source 2]. * Nipple discharge that is not breast milk [Source 1]. * Persistent breast pain or tenderness that does not go away [Source 1]. Regular breast cancer screenings, such as mammograms, are also vital for early detection, even if you don't have any symptoms [Source 2]. Discuss with your doctor when you should begin screening and how often you should be screened based on your personal risk factors.

Frequently asked questions

Does HER2-negative breast cancer mean my cancer is less aggressive?

Not necessarily. While HER2-negative cancers don't have the aggressive growth driven by the HER2 protein, their aggressiveness depends on other factors. For example, triple-negative breast cancer, a HER2-negative subtype, is often more aggressive than other types and can grow and spread quickly [Source 1, Source 2].

Can HER2-negative breast cancer become HER2-positive over time?

It is rare for a HER2-negative breast cancer to become HER2-positive. However, if breast cancer recurs or spreads, doctors may retest the HER2 status of the new tumor. This is because, in some cases, the cancer cells can change their characteristics, which might influence treatment decisions [Source 2].

What is triple-negative breast cancer, and how does it relate to HER2-negative?

Triple-negative breast cancer (TNBC) is a specific type of HER2-negative breast cancer. It is called "triple-negative" because its cells also lack estrogen receptors (ER) and progesterone receptors (PR), in addition to being HER2-negative [Source 1, Source 2]. TNBC accounts for about 10% to 15% of all breast cancers and requires different treatment approaches [Source 2].

Are there any targeted therapies for HER2-negative breast cancer?

HER2-negative breast cancer does not respond to therapies specifically targeting the HER2 protein. However, for certain subtypes like triple-negative breast cancer, newer targeted therapies such as PARP inhibitors and immunotherapies are available for some patients, depending on specific tumor characteristics [Source 1, Source 3].

How often should I get screened for breast cancer if I'm HER2-negative?

The frequency of breast cancer screenings, such as mammograms, depends on your age, personal risk factors, and family history, not specifically on a HER2-negative diagnosis (unless you've already had breast cancer). Your doctor will recommend a personalized screening schedule to ensure early detection [Source 2].

Does being HER2-negative mean I won't need chemotherapy?

No, being HER2-negative does not mean you will avoid chemotherapy. Chemotherapy is a common and effective systemic treatment for many HER2-negative breast cancers, especially if they are larger, have spread to lymph nodes, or are triple-negative [Source 1, Source 3]. Your treatment plan will depend on your cancer's specific characteristics.

Sources

• MedlinePlus — HER2-Negative Breast Cancer
• Mayo Clinic — HER2-Negative Breast Cancer
• Cochrane Library — HER2-Negative Breast Cancer