What Is HER2-Positive Breast Cancer?
About 20% to 25% of breast cancers are HER2-positive. That means they have a certain protein (HER2/neu) that makes cancer cells grow. This kind of cancer tends to be much more aggressive and fast-growing than other kinds of breast cancer, but there are effective treatments that target HER2.
Your doctor will test your cancer to find out if yours is HER2-positive and also check on whether it has spread and if it's sensitive to hormones.
Researchers aren't sure what causes breast cancer. They think it may be a combination of things, including your genes, your environment, and your lifestyle. Every case is different.
In HER2-positive breast cancer, a gene causes cancer cells to make too much HER2/neu protein. When that happens, cancer cells grow in an out-of-control way.
This only happens in cancer cells. It can happen in other cancers, too -- not just breast cancer.
You can't inherit a bad copy of this gene from a parent or pass it on to your children.
The most common symptom of any type of breast cancer is a lump in your breast that feels different from the area around it.
Other symptoms include:
- Breast swelling or a change in the shape of the breast
- Skin irritation or dimpling
- Pain in the breast or nipple
- Redness or thickness of the nipple or breast skin
- Discharge from the nipple (not breast milk)
You may have noticed a difference in your breasts during a self-exam, or you may have had a mammogram that showed the cancer.
Getting a Diagnosis
When you're diagnosed with breast cancer, your doctor will test for HER2. There are four types of tests for HER2-positive breast cancer.
The IHC test (immunohistochemistry) checks for how much HER2 protein is in a sample of breast cancer tissue.
Three other tests check to see if there are too many HER2 genes in the cancer cells:
- FISH test (fluorescence in-situ hybridization)
- SPOT-Light HER2 CISH test (subtraction probe technology chromogenic in-situ hybridization)
- Inform HER2 Dual ISH test (inform dual in-situ hybridization)
Sometimes the results of one test aren't clear, and your doctor may order another type of test.