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About 1 of every 4 of breast cancers are HER2-positive. That means the cancer cells have more of the protein HER2. It causes these cells to grow and spread faster than the ones with normal levels of the protein.

This cancer is more aggressive than other types, but there are treatments to help. You’ll work together with your doctor to come up with a treatment plan that's best for you.


Researchers aren't sure what causes breast cancer. They think it may be a combination of things, including your genes, environment, and lifestyle. But genes don’t play the same role in HER2-positive cancer as they do with other kinds. You can't inherit a bad copy of this gene from a parent, and you won’t pass it on to your children.


The most common warning sign of any type of breast cancer is a lump in your breast that feels different from the area around it.

Other symptoms may include:

  • Breast swelling
  • A change in its shape
  • 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 a growth.

Getting a Diagnosis

If you're diagnosed with breast cancer, your doctor will check to see if you have HER2. He’ll probably give you one or more of these tests:

The IHC test looks for how much HER2 protein is in a sample of breast cancer tissue.

These tests see if there are too many HER2 genes in the cancer cells:

  • FISH test
  • SPOT-Light HER2 CISH test
  • Inform HER2 Dual ISH test

Sometimes the results of a single test aren't clear. If that happens, your doctor may order another type.

Questions for Your Doctor

  • How are you sure my cancer is HER2-positive?
  • Where exactly is my cancer?
  • What stage is it?
  • What are my treatment options?
  • What treatment do you think will work best for me?
  • How quickly do I need to start treatment?
  • How will treatment make me feel?
  • Is there a clinical trial that I should consider?
  • Will I be able to work?
  • Do I need to have my breast removed?
  • Do I need radiation?
  • Do I need chemotherapy?
  • Do I need hormone treatment?
  • Will my insurance cover my treatment?
  • What if my cancer doesn’t respond to treatment?