Breast cancer cells may have receptors (proteins) that hormones or a protein called HER2 can attach to and encourage the cells to grow. A pathologist tests the cancer cells that were taken during the biopsy or surgery for these receptors.
The results help you and your doctor decide on the most effective treatment for you.
Hormones help control how cells grow and what they do in the body. All men have small amounts of the hormones oestrogen and progesterone in their bodies. Hormones, particularly oestrogen, can encourage breast cancer cells to grow.
Most oestrogen in men is made from male sex hormones (androgens). The testicles make a small amount.
Breast cancer that has oestrogen receptors is called oestrogen receptor-positive or ER-positive breast cancer. The term ER is used because the American spelling of oestrogen is estrogen. Some hospitals also check if cells are progesterone receptor positive (PR-positive).
Most breast cancers in men are ER positive and they respond well to hormonal treatments.
Some breast cancers have too much of a protein (receptor) called HER2 (human epidermal growth factor receptor 2) on the surface of their cells. This is called HER2-positive breast cancer. The extra HER2 protein encourages the cancer cells to divide and grow.
It is usually treated with a targeted therapy drug, for example, trastuzumab (Herceptin®). HER2 positive breast cancer is uncommon in men.