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It is a common cancer found mainly in women, but men can get it too. For every 100 women with breast cancer there is one man who has the disease.
Breast cancer most often affects women who have been through the menopause. Younger women can get it, but it is not common in the under 50s.
We don't know exactly what causes breast cancer, but you may be more at risk if…
- you are very overweight
- you had your first pregnancy after the age of 35
- you have never been pregnant.
In about 1 in 20 cases the cancer may have been passed on through the family. If you have close relatives (mother, sister or daughter) who have had breast or ovarian cancer, you may be more at risk.
Smoking may increase your chances of getting breast cancer, but this is not known for certain.
We think that hormone replacement therapy (HRT), if taken for more than 10 years, may slightly increase the risk of breast cancer. The risk is very small, and it needs to be weighed against the benefits HRT can bring.
Some women worry that a knock or injury to the breast can cause cancer. There is no evidence at all that this is the case.