These proteins act as receptors on breast cells and are important for maintaining a healthy cell lifecycle. Normally, human epidermal growth factor receptor 2 (HER2) helps control how a healthy breast cell divides, grows, and repairs itself. However, when the HER2 gene is abnormal, it causes the cells to divide and grow at an uncontrolled rate.
HER2-positive breast cancer is a more aggressive type of breast cancer compared with HER2-negative types. Excessive amounts of the gene, and the protein receptors it produces, encourage the rapid growth of cancer cells.
There is a genetic cause of HER2-positive breast cancer.
At the moment, doctors are not sure exactly what causes HER2 gene abnormalities. Some ideas on its origin include:
Though there may be genetic components, experts believe that it is not possible to inherit a bad HER2 gene from a parent, so it is not hereditary.
Prevalence, diagnosis, and early detection
HER2-positive breast cancer tends to grow faster, spread more easily, and is more likely to come back than HER2-negative breast cancer.
Symptoms of HER2-positive breast cancer are the same as for any other type of breast cancer. The most typical sign is a lump in the breast that is harder than the surrounding area.
Other symptoms may include:
- change in breast shape
- breast swelling
- discharge from the nipple that is not breast milk
- pain in the breast or nipple
- redness or thickness of the nipple or breast skin
- skin irritation or dimpling
Detection of breast cancer can happen at home with a self-exam or at a doctor's office with a mammogram. Once diagnosed, the doctor will run tests to determine if the lump is breast cancer, and from there, will determine if the cancer is HER2-positive.
Tests for HER2
There are four main tests that doctors use to determine if a woman has HER2-positive cancer. These tests include:
- FISH (fluorescent in situ hybridization) test - a positive or negative test used to discover if there is an excess of the HER2 gene in breast cancer cells.
- IHC (immunohistochemistry) test - this test determines if there is too much HER2 protein in breast cancer cells. A score of 0 or 1+ is negative, 2+ is borderline, and 3+ is positive.
- Inform HER2 dual ISH test - this test shows if breast cancer cells are HER2-positive.
- SPoT-Light HER2 CISH test - this identifies whether there are too many copies of the HER2 gene in breast cancer cells.
A failed test can result in misdiagnosis, which could mean a HER2-positive breast cancer is not detected. People should ask their doctor how confident they are in the results and should ask for additional testing if a result comes back as borderline. Also, if needed, a person should seek out a second opinion.
Kadcyla, a form of targeted chemotherapy, may be used in the treatment of chemotherapy.
HER2-positive breast cancer cells do not respond well to hormone treatment. However, there are several other treatment options available. The doctor will help determine which of these treatments is best.
HER2-positive breast cancer treatments can include:
- Kadcyla - a form of targeted chemotherapy.
- Tykerb - a chemical that targets HER2-positive breast cancer cells.
- Perjeta - blocks the HER2-positive cancer cells ability to receive signals to grow.
- Herceptin - also blocks growth signals to HER2 positive cancer cells.
In addition to treatment, people diagnosed with HER2-positive breast cancer should make sure they live healthfully. This includes:
- Diet - obesity and diabetes have a correlation in the incidence of breast cancer.
- Exercise - physical activity promotes general health, and helps prevent a range of conditions.
- Lifestyle - smoking and excessive alcohol use increase the risk of developing cancer and a wide variety of other conditions.
People diagnosed with HER2-positive breast cancer should seek out support from friends and family, ask questions of their doctors, exercise as well as they can, and stay nourished.
Most of all, it is important for them to remember they can take an active role in how they are treated for HER2-positive breast cancer.
Survival rates and statistics
HER2-positive cancer cells are present in roughly 25 percent of all breast cancer cases. Women with HER2-positive cells are more likely to be younger and have a more aggressive form of breast cancer.
In general, breast cancer survival rates are broken down across five stages from 0-4. According to the American Cancer Society, the 5-year life expectancy is as follows:
- stage 0 - close to 100 percent
- stage 1 - close to 100 percent
- stage 2 - 93 percent
- stage 3 - 72 percent
- stage 4 (the metastatic stage) - 22 percent
The earlier the breast cancer is discovered and treated, the better chances of survival the person has.
The length of time a person with breast cancer will survive depends on:
- the individual
- how advanced the cancer is
- when it is discovered
- how it is treated
HER2-positive tends to be a more aggressive cancer compared with hormone positive cancers and triple negative cancers. Hormone positive cancers, such as estrogen receptor-positive (ER-positive) or progesterone receptor-positive (PR-positive) breast cancer may also be present for people with HER2-positive breast cancer. In those cases, treatment would need to target both of the problem areas. When HER2-positive breast cancer is caught and treated early, people can have an overall good outlook.