How does the test work?
The testing lab typically uses a specialized staining process on the breast tissue sample to see if hormone receptors are present. The technical name for this procedure is an “immunohistochemical staining assay” or an “ImmunoHistoChemistry (IHC).” Findings will be included in a pathology report given to your doctor. If the cancer is deemed “estrogen-receptor-positive” (ER+), its cells have receptors for the estrogen hormone. That means that the cancer cells likely receive signals from estrogen to promote growth. About two out of every three breast cancers contain hormone receptors.
If the cancer is progesterone-receptor-positive (PR+), its cells have receptors for the progesterone. This hormone could then promote the growth of the cancer.
What do the results of hormone testing mean?
Breast cancer patients who test positive for both estrogen receptors and progesterone receptors usually have a better-than-average prognosis for survival and a complete recovery than those who have no receptors present. Also, the more receptors and the more intense their reaction, the better they respond to hormone therapy. Patients with one type of receptor but not the other may still reap benefits from this form of treatment, but likely not to the same degree. As mentioned earlier, if the cancer is both ER- and PR-negative, it probably won’t respond to hormone therapy. Typical response rates to hormone therapy are as follows:
ER and PR positive: 75-80%
ER positive and PR negative: 40-50%
ER negative and PR positive: 25-30%
ER negative and PR negative: 10% or less
Similar to the hormone receptor test, the HER2/neu test looks for a specific kind of protein that is found with certain types of cancer cells and the gene that produces it. The formal name of that gene is the human epidermal growth factor receptor 2, and it makes HER2 proteins. These proteins are receptors on breast cells.
In a sense, genes contain the formula for the number and combination of proteins a cell needs to remain healthy and function properly. Certain genes and the proteins they create can determine how breast cancer progresses, as well as how it responds to various types of treatment.
What is a HER2 receptor and how does it relate to breast cancer?
Healthy HER2 receptors are the proteins that help manage how a breast cell grows, divides, and repairs itself. However, in about a quarter of all breast cancer patients, the HER2 gene isn’t functioning properly. It makes an excess number of copies of itself in a process known as “HER2 gene amplification.” Then these extra genes instruct the cells to make too many HER2 receptors, which is called “HER2 protein overexpression.” The ultimate result is that breast cells grow and divide in an uncontrolled fashion.
The HER2/neu test can discover whether the sample is normal or whether it has too much of the HER2/neu protein or an excessive number of copies of its gene. If you have been diagnosed with invasive breast cancer or have had recurrent breast cancer, your doctor may recommend this test. It will help your medical team determine your prognosis, characteristics of the tumor including how aggressive the tumor is likely to be, and the best treatment options.
This test is often ordered in conjunction with the hormone receptor test. Typically, the breast cancer tissue sample from a biopsy or the tumor removed during a mastectomy is used.