Some breast cancer cells test positive for a type of hormone receptor which are actually proteins that are found in the inner and outer surfaces of the cells. If present, these receptors attach themselves to either estrogen or progesterone hormones, and these hormones fuel the growth of the breast cancer.
ER-positive breast cancers have estrogen receptors, and PR-positive breast cancers have progesterone receptors. Oncologists can order tests on tissue samples of tumors taken from the breast to identify if a receptor is present so they will know how to correctly treat the disease. Some cancer treatments can work by blocking the receptors’ ability to attach to hormones, which can stop the cancer from growing and spreading to surrounding tissues in the breast or other parts of the body.
Oncologists will also test HER2/neu levels in breast cancer tumors. HER2/neu is a protein that is on the outside of all breast cells. If the levels are found to be higher than normal, the breast cancer is referred to as HER2-positive, and these cancers have more aggressive growth, and can spread faster. If the levels are lower than normal, the cancer is categorized as HER2-negative.
When the cancer is diagnosed as HER2-positive, it can be treated more successfully with drugs that specifically target this protein. HER2-negative cancers do not respond to this type of treatment.
Triple Negative Breast Cancer
Triple negative breast cancer does not have hormone receptors. Unlike other types of breast cancer, it is not dependent on hormones for growth and the cancer cells don’t over-produce the HER2 protein.
The name, triple negative, refers to breast cancer that is estrogen receptor negative (ER-), progesterone receptor–negative (PR-), and HER2 receptor-negative (HER2-). It is a more complex disease, and the medications used to block the estrogen and progesterone hormones and the HER2 protein are not as effective in treating it. There are, however, a number of other chemotherapy drugs that are used, usually in combination with both surgery and radiation.
While anyone can be diagnosed with this type of cancer, it is typically seen in a younger population of women (under age 50). Both African American and Hispanic populations and people with a BRCA1 gene mutation are at a greater risk.
Triple negative breast cancer is more aggressive, more likely to spread, and has a higher incidence of recurrence.