HER2-positive breast cancer is a type of breast cancer that has a protein called human epidermal growth factor receptor 2. This receptor helps the cancer cells grow.
Some types of breast cancers go through a gene alteration that creates extra HER2 protein. HER2-positive breast cancers are typically aggressive when compared with other forms of breast cancer.
HER2-positive breast cancer is not inherited from genetics but instead, is a somatic genetic mutation. Somatic gene mutations are acquired by a cell that can be passed to the progeny of the mutated cell during cell division. If the patient has a close relative with HER2-positive breast cancer, it does necessarily mean that the patient’s risk is increased for this type of cancer.
HER2-positive breast cancers may benefit from anti-HER2 drugs. Such drugs directly target the HER2 receptor. HER2 targeted therapy is not used for HER2-negative cancers.
HER2 status helps to guide treatment for patients. This is often included in a patient’s pathology report, and tells the patient whether or not HER2 is playing a role in their cancer via a biopsy or surgery sample of the cancer. Any tumors present should be tested for HER2 status using the following:
- Immunohistochemistry (IHC) tests detect receptors in the cancer cells.
- Fluorescence in situ hybridization (FISH) tests HER2 genes in the cancer cells.
More often than not, the IHC test is completed first. If the score is unclear according to the test results grading system, the tumor is sent for FISH testing to confirm the status. If a patient’s HER2 test results appear to be borderline, it is recommended to ask for another HER2 test to confirm the status.