HER2(human epidermal growth factor receptor 2) is a growth-promoting protein present on the outside of all breast cells. Breast cancer cells with higher than normal levels of HER2 are called HER2-positive.
HER2 (human epidermal growth factor receptor 2) is a gene that can play a role in the development of breast cancer. Information about HER2 status can tell you whether or not HER2 is playing a role in the cancer.
There are several tests used to find out if breast cancer is HER2-positive. Two commonly used tests are:
FISH is more expensive and takes longer to get the results. Often the IHC test is done first.1,2
Interpreting the IHC test result score:1
| IHC Score | HER2-positive or negative | Treatment / Course of Action |
|---|---|---|
| 0 or 1+ | HER2-negative | Does not respond to treatment with drugs that target HER2 |
| 3+ | HER2-positive | Usually treated with drugs that target HER2 |
| 2+ | Equivocal / unclear | HER2 status needs to be clarified/ futher testing required |
With the FISH test, you get a score of either positive or negative (some hospitals call a negative test result “zero”).2
HER2 positive breast cancers tend to grow and spread faster than other breast cancers, but are more likely to respond to treatment with drugs that target the HER2 protein.
