Human epidermal growth factor receptor 2 (HER2) is a gene that makes proteins in the breast. It can play a role in the development of breast cancer.

HER2 proteins act as receptors on breast cells and play a key role in the life cycle of breast cells. Usually, HER2 helps control how a healthy breast cell divides, grows, and repairs itself. However, changes in the HER2 gene can cause the cells to divide and grow uncontrollably.

HER2-positive breast cancer is an inherently more aggressive type of breast cancer than HER2-negative types. High levels of the HER2 gene and the protein receptors it produces encourage the rapid growth of cancer cells. However, highly effective treatment is now available for this type of cancer.

In this article, learn more about HER2-positive breast cancer, how doctors identify it, and which treatments are available.

Fast facts on HER2-positive breast cancer:

  • HER2 is a gene that plays a role in the development and aggressiveness of breast cancer.
  • Overexpression of the gene results in increased tumor growth.
  • Targeted therapies are effective treatment options for HER2-positive breast cancer.
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HER2 is a protein present on the outside of breast cells. It plays a role in the life cycle of healthy cells. However, a problem with this gene can cause cells to reproduce too quickly, leading to cancer.

There are two types of HER2-positive breast cancer. The following table summarizes the differences between them and notes their frequency, according to the Surveillance, Epidemiology, and End Results (SEER) program.

NameHigh levels of HER2Receptors for estrogen and progesteronePercentage of female breast cancer cases
HR+/HER2+ (luminal B)YesYes10%
HR-/HER2+ (HER2-enriched)YesNo4%

Receptors for the hormones estrogen or progesterone on a tumor can promote tumor growth.

A doctor may recommend tests for breast cancer if a person notices symptoms or if a mammogram shows changes in their breast tissue. If tests confirm that cancer is present, further tests can then help determine if it is HER2-positive.

Symptoms of HER2-positive breast cancer are the same as for any other type of breast cancer. They include:

  • a new lump in the breast or armpit
  • changes in breast shape, size, or texture
  • flaky skin on the nipple or breast
  • discharge from the nipple that is not breast milk
  • inverted nipple
  • pain in the breast or nipple
  • skin irritation or dimpling

Learn more about the signs and symptoms of breast cancer here.

What does testing involve?

If a doctor confirms an unusual growth, they will take a biopsy. To collect a sample, they may perform one of the following procedures:

  • Use a fine needle to remove a sample of breast cells or a liquid in fine-needle aspiration.
  • Use a larger needle in a core needle biopsy.
  • Carry out minor surgery as an outpatient procedure.

According to the American Cancer Society, a core needle biopsy is often the preferred option.

The doctor will send the tissue samples to a laboratory to test whether or not breast cancer is present. If it is, the pathologist will test to see if the cancer is HER2-positive.

The two main tests for determining whether or not HER2-positive cancer is present are the fluorescent in situ hybridization (FISH) test and the immunohistochemistry (IHC) test.

The FISH test looks for additional copies of the HER2 gene in breast cancer cells. It uses special labels that attach to the HER2 proteins that glow in the dark.

The IHC test uses a chemical dye to stain HER2 proteins and can determine how much HER2 protein is present in breast cancer cells.

Often, the pathologist will carry out the IHC test and then the FISH test. IHC testing is faster and less costly than FISH testing. However, if the results of the IHC test are unclear, a person will need a FISH test to determine whether or not a tumor is HER2-positive.

Why is early detection important?

Receiving early treatment can improve the outcome for people with HER2-positive and other types of breast cancer.

For this reason, it is best to get an early diagnosis and start treatment as soon as possible.

Test results

Results for the IHC test will show a score of 0 or 1+ (negative), 2+ (borderline), or 3+ (positive).

FISH tests results will be either positive or negative, sometimes called “zero.”

The results will help the doctor decide on the best approach for treatment, as some medications specifically target HER2-positive breast cancers.

Various treatment options are suitable for treating HER2-positive breast cancers, depending on the type and stage. The doctor will work with the individual to determine a treatment plan.

Options include:

Medications for treating HER2-positive breast cancer include:

The exact drug or combination of drugs a person receives may vary depending on the stage of their cancer.

If HER2-positive breast cancer is HR+/HER2+, meaning that the tumor has receptors for the hormones estrogen or progesterone, treatment may also include hormone therapy.

For people with metastatic breast cancer, a doctor may prescribe a combination of chemotherapy and drugs that specifically target HER2-positive breast cancer.

A relative survival rate helps give an idea of how long a person with a particular condition will live after receiving a diagnosis compared with those without the condition.

For example, if the 5-year relative survival rate is 70%, it means that a person with the condition is 70% as likely to live for 5 years as someone without the condition.

It is important to remember that these figures are estimates. A person can talk with a doctor about how their condition is likely to affect them.

Some factors affecting a person’s survival rate with breast cancer include:

  • individual factors, such as the person’s age and overall health
  • the stage of the cancer at diagnosis
  • the treatment the person receives

HER2-positive cancers are more aggressive than HER2-negative cancers. With treatment, however, the chances of survival are high, especially with an early diagnosis. In some cases, they may be higher than for HER2-negative breast cancer due to effective targeted treatment.

According to the SEER program, the likelihood of living for another 5 years with HER2-positive cancer, compared with a person who does not have breast cancer, is as follows. These statistics are based on figures for the years 2011–2017.

localized, meaning the cancer is still in its original location98.9%96.7%
regional, meaning the cancer has spread to nearby tissues89.4%82.0%
distant, meaning the cancer has affected organs throughout the body44.7%37.9%

What happens at each stage of breast cancer? Find out here.

Some people with breast cancer have high levels of a gene called HER2, so doctors call this HER2-positive breast cancer. It is inherently more aggressive than some types of breast cancer, but targeted therapies can treat it effectively.

People who have symptoms that may indicate breast cancer may undergo a biopsy. Pathologists will use the sample to find out if HER2 levels are high, and a doctor will recommend a treatment plan accordingly.