Updated: May 16, 2020

Her2 Positive Breast Cancer is part of a larger HER family.

I was sitting in the audience when all of a sudden a slide popped up with “HER3” on it! Throughout my journey with breast cancer, I’ve been focusing on HER2. It’s the one we hear about most often. During our initial biopsy, oncologists and pathologists usually test to see if the tumor is either HER2+, HER2-, or sometimes, it comes back unequivocal. Before I go any further, let’s talk a bit about what HER2 actually is.

What is HER2?

HER2 is also known as the Human Epidermal Growth Factor (HEGF) receptor 2. The HER2 gene makes HER2 proteins which control how healthy breast cells grow, divide and repair themselves. However, in ~20% of those diagnosed with breast cancer, the HER2 gene doesn’t work properly and reproduces too many copies of itself which lead to the breast cells growing and dividing in uncontrollable ways (referred to as HER2 gene amplification and HER2 protein over-expression), or HER2+ Positive breast cancer.

The good news is that with HER2 positive breast cancer, there are receptors on these proteins that usually respond well to treatment. The most common drugs include:

· Herceptin (chemical name: trastuzumab);

· Kadcyla (chemical name: T-DM1 or ado-trastuzumab emtansine);

· Nerlynx (chemical name: neratinib);

· Perjeta (chemical name: pertuzumab);

· Tykerb (chemical name: lapatinib).

I was treated with both Herceptin + Perjeta. (You can read more about these drugs in our blog here).


The ErbB protein family consists of 4 members

  • ErbB-1, also called HER1

  • ErbB-2, also called HER2

  • ErbB-3, also called HER3

  • ErbB-4, also called HER4

The HER family can play a role into why some people are resistant to hormonal therapies. Without a scientific background, I have more questions than answers but I am excited to reach out to the medical professionals to help us understand this relationship. Stay tuned for details to come! I am just as curious as you are!

Until then here are a few articles which speak to HER1, HER2, HER3, and HER4:

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