Some Breast Cancers May Switch HER2 Status if They Come Back

Moderators

Some Breast Cancers May Switch HER2 Status if They Come Back
May 18, 2021
If breast cancer comes back — called recurrence by doctors — the HER2 status of the recurrent cancer may change from HER2-positive or HER2-negative to a new classification of HER2 status, called HER2-low. Read more...

Horse2310

My question pertains to HER 2LOW...I was diagnosed 2 years ago..strong ER postive..stage 1 grade 1 1 CM...lumectomy/rads/arimidex...when I look at my pathology, the ICH test says equivical and I had to get the FISH test...which came back negative...I think the ratio said 1.1.......the ICH test had numbers that were 2.1 and 2.4..does this mean Iam boderline for HER2?...am I higher risk if Im borderline? should I have been treated with another drug?

thanks

Moderators

Hello, Horse2310, and welcome to Breastcancer.org! We're sorry you have to be here, but we're really glad you've found us!

The FISH test is the most accurate test to determine if the cancer is HER2-positive, but it is more expensive and takes longer to return results. This is why an IHC test is usually the first test done. As you can read in our main site, "generally, only cancers that test IHC 3+ or FISH positive respond to the medicines that target HER2-positive breast cancers." You can read the whole article here: HER2 Status

Hope this helps!

The Mods

Horse2310

Thank you so much for your response ...it really helps.. I thought I did read that you can be her 2 low with a negative fish test though?

Thanks

Moderators

Hi again Horse2310,

Yes, you're correct. According to this research news article:

"HER2-low breast cancers have levels of HER2 proteins that are too low to be considered positive. They have IHC scores of 1+ or 2+ or a FISH score of negative. About half of breast cancers classified as HER2-negative have low HER2 expression."

Does this help?

Edited to add: Per your question about whether or not you should have been treated with another drug. This is also from that article:

"Studies are underway to see if HER2-low breast cancers could be treated with anti-HER2 medicines, such as Herceptin (chemical name: trastuzumab) or Enhertu (chemical name: fam-trastuzumab-deruxtecan-nxki)."

We hope this helps!

--The Mods