How are HER2 breast tumors tested?

HER2 stands for human epidermal growth factor receptor 2. This is a gene that makes a protein found on the surface of all breast cells. It is involved in normal cell growth. The pathology report includes information about HER2 status to help determine if HER2 plays a role in cancer.
The HER2 gene makes the HER2 protein. HER2 proteins are receptors on breast cells. Normally, the HER2 receptor helps control how healthy breast cells grow, divide, and repair themselves. But in about 10-20% of breast cancers, the HER2 gene doesn't work properly and makes many copies of itself (HER2 gene amplification). All of these extra HER2 genes cause breast cells to make too many HER2 receptors (HER2 protein overexpression). This causes breast cells to grow and divide uncontrollably.
Breast cancers with HER2 gene amplification or HER-positive overexpression tend to grow faster, and have a higher chance of recurrence than other cancers.

There are several tests used to find out if breast cancer is HER2 positive. Some of the most common HER2 breast cancer tests are:
2.1. IHC test The IHC method uses a chemical dye to stain the HER2 protein. The IHC gives it a score of 0 to 3+, measuring the amount of HER2 protein on the surface of cells in a sample of breast cancer tissue. A score between 0 and 1+ is considered HER2 negative. If the score is 2+, then it is considered right on the border between negative and positive. A score of 3+ is considered HER2 positive.
If the test scores 2+, additional FISH testing is required to be performed on the cancer tissue sample to determine if the cancer is HER2 positive.

2.2. FISH test This FISH test uses special labels that attach to the HER2 protein. These special labels contain chemicals that change color and glow in the dark when attached to HER2 proteins. This is the most accurate test, but it is more expensive and takes longer to get results. So that's why the IHC test is often used first to make a diagnosis of HER2-positive breast cancer. With the FISH test, either a positive or negative score is obtained (negative results in a zero). It is important to know which HER2 test is available. Only cancers that test positive for IHC3+ and FISH respond to drugs that target HER2-positive breast cancers. Studies have shown that some HER2-positive breast cancers can become negative. calculate HER2 over time. And similarly, HER2-negative breast cancers can become positive over time. If breast cancer recurs in the future as well as the disease progresses, the doctor will now use another biopsy sample and check the condition of the HER2 tissue.

Research has shown that some HER2 status test results may not be correct. This may be because different laboratories have different rules for classifying HER2 positive and negative status. Furthermore, each pathologist may also use different criteria to decide whether a result is negative or positive. In most cases, this happens when the test results are borderline - meaning HER2-positive or HER2-negative.
In other cases, tissue in one area of ​​breast cancer can test for HER2 positive and conversely tissue in another area of ​​breast cancer can test for HER2 negative.
If the HER2 test result is HER2 negative, doctors will not recommend anti-HER2 treatment. Although, patients are likely to benefit from those drugs. Conversely, if breast cancer is HER2-negative but the test results classify it as HER2-positive, inaccuracies can leave women diagnosed with breast cancer without the best possible care. If all or part of your breast cancer is hER2-positive but your stool test results are not positive, your doctor will recommend anti-HER2 therapy. Although, you may not be sure you will get any benefit from this medicine.

In cases where HER2 test results are borderline, additional combined tests are required for the most accurate results.
Breast cancer is a common cancer in women. If detected late, treatment will be more difficult than with early detection. Therefore, for subjects at risk, it is necessary to screen for breast cancer early to improve the chances of cure and limit recurrence.
Currently, Vinmec International General Hospital has been implementing a Breast Cancer Screening Package for women of different ages. At Vinmec, there are all necessary medical equipment to carry out the methods of examination, diagnosis, testing, imaging, and treatment performed by a team of highly qualified and experienced medical doctors. through training and technical certification, can handle quickly and efficiently. Therefore, when using Vinmec's breast cancer screening and early detection package, customers can detect cancer even when there are no symptoms.
For detailed advice on breast cancer screening packages as well as effective treatment methods at Vinmec, please come directly to Vinmec health system nationwide or register online HERE .
References: cancer.org, webmd.com