Risk factors for male breast cancer

Male breast cancer is thought to be caused by a combination of factors, though the exact causes remain unclear.

Scientists researching male breast cancer have, however, identified age, genetics, exposure to ionising radiation and hormone imbalances as major risk factors.

As with many diseases, the risk of breast cancer increases as we get older. Most men who develop breast cancer in England are over 60.

Up to 2 in 5 of male breast cancer cases involve inherited faults in the breast cancer genes BRCA1 and BRCA2. This means men with breast cancer are four times more likely  to have the hereditary form than women with the disease.

If you have a family history of breast cancer, you may be at an increased risk yourself. Ask your GP to help you work out what increased risk, if any, you may have – and how you can minimise it.

If you have ionising radiation therapy - to treat cancer in the chest for example – this could increase your risk of breast cancer. The increase is thought to be less severe for men than women and exposure to ionising radiation is believed to affect very few men overall.

Men normally produce high levels of androgens – or male hormones - such as testosterone, and low levels of the female hormone, oestrogen. Oestrogen promotes the growth of many breast cancers in both women and men.

Raised oestrogen levels and decreased androgen levels can increase a man’s risk of developing breast cancer. Here are some of the conditions that can cause hormone imbalance.

Klinefelter’s Syndrome, a rare genetic condition where a male is born with an extra female chromosome. A man with Klinefelter’s syndrome can have risk of breast cancer 20 – 60 times greater that of men unaffected by the condition.

Liver cirrhosis, a condition which increases oestrogen levels and reduces testosterone levels in men.

Obesity. Fat cells can convert male hormones into oestrogen. With a greater number of fat cells in their bodies, obese men will produce a correspondingly higher amount of oestrogen.

Testicular disorders, such as mumps in adulthood or undescended testes. These can reduce the production of male hormones and raise relative oestrogen levels.

Oestrogen therapy, used to treat some prostate cancers. While oestrogen therapy may increase the risk of male breast cancer, however, the risk is small and far outweighed by the benefits of treating prostate cancer.

Men who are undergo a sex change take high levels of oestrogen, which suggests that they may be at increased risk of developing breast cancer.