Although HER2-positive breast cancer has a genetic element, it is not hereditary. Inheritable gene mutations that may increase the risk of breast cancer include mutations in the BRCA1 and BRCA2 genes.
HER2 stands for human epidermal growth factor receptor 2. The HER2 gene contains instructions for making proteins that healthy breast cells need to function normally.
HER2 receptors influence the growth, division, and repair of breast cells. In some people, the HER2 gene does not work properly, which can result in the growth of a HER2 breast tumor.
This article will take a closer look at what causes HER2-positive breast cancer, inherited genes that may increase the risk of breast cancer, symptoms, diagnosis, and more.
The HER2 gene does not function as it should in
When this occurs, breast cells make too many HER2 receptors, which doctors call HER2 protein overexpression. Protein overexpression causes the breast cells to grow and divide uncontrollably.
HER2-positive breast tumors usually grow faster and have a higher risk of spreading and recurring than HER2-negative breast tumors.
While a person’s genes can contribute to their risk for HER2-positive breast cancer, the
Additionally, a 2016 cohort study concluded that people who are younger than 41 when they receive a HER2-positive breast cancer diagnosis and have no family history of breast cancer have a low chance of being a high risk gene carrier.
Learn more about HER2-positive breast cancer.
Inherited breast cancer
Parents can pass on other genetic mutations that give their children a higher risk of breast cancer. The ACS suggests that
The most common cause of inherited breast cancer is a BRCA1 or BRCA2 gene mutation.
The ACS states people with these gene mutations have a 7 in 10 chance of developing breast cancer by age 80. The more family members that have had breast cancer, the higher a person’s risk.
Other gene mutations can also cause inherited breast cancer, but they are less common and do not increase a person’s risk of developing breast cancer as much as BRCA1 or BRCA2. These include:
- a new lump in the breast or armpit
- thickening or swelling of part of the breast
- irritated or dimpled breast skin
- redness or flaking skin around the nipple or breast
- pulling in of the nipple
- pain around the nipple
- discharge from the nipple that is not breast milk
- a change in the size or shape of the breast
- pain in any area of the breast
Doctors may use a range of tests to find out whether breast cancer is HER2-positive. The two most common tests are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH).
IHC involves taking a breast tissue sample and staining the HER2 proteins with dye. Doctors then have a measure of the volume of HER2 proteins on the surface of the breast cells. IHC test scores are as follows:
- HER2-negative: 0–1+
- Borderline: 2+
- HER2-positive: 3+
In cases of borderline IHC results, doctors usually follow up with a FISH test to determine whether the cancer is HER2-positive or HER2-negative.
FISH involves attaching labels to HER2 proteins. These labels can change color and glow in the dark when they attach to HER2 proteins.
The FISH test is more accurate and returns a binary, positive or negative, test result. However, it is more expensive and time-consuming, so doctors usually start with the IHC test.
- maintaining a healthy body weight
- getting regular exercise
- limiting or avoiding alcohol
- breastfeeding, if possible
Additionally, a person with a family history of breast cancer or inherited mutations in the BRCA1 and BRCA2 genes can talk with their doctor about additional ways to reduce their risk.
The HER2 gene contains the instructions for making proteins necessary for healthy and properly functioning breast cells. A person’s genes can contribute to their risk of developing HER2-positive breast cancer, but the gene mutation is not hereditary.
Doctors may use immunohistochemistry and fluorescence in situ hybridization tests to diagnose HER2-positive breast cancer.
People can reduce their risk of developing breast cancer by maintaining a healthy weight, staying physically active, and avoiding alcohol.