Women with a family history of breast cancer are four times more likely to develop breast cancer than other women - even if they don't have high-risk genes, according to a new study.
For the study, scientists looked for the first time at the risk of getting the disease for women who do not have a faulty gene but have family members who have developed breast cancer.
About one in six women with breast cancer have a family history of the disease, which means about 13 per cent of all sufferers have a strong family record of it, but do not have a faulty gene.
The researchers looked at women who had one first- degree relative - mother, daughter or sister - under the age of 50 with breast cancer and at least one other relative like a cousin or aunt with breast cancer, or three relatives of any age with the disease.
They found that although the risk of breast cancer in the general population was one in nine, for the group studied the risk rose to more than one in three.
According to the researchers, a significant family history of breast cancer alone could be strong enough grounds for doctors to offer preventative treatments.
"This is the first time the breast cancer risk for this group of women has been measured, and it's significantly higher than that of the general population," the Daily Express quoted lead author Dr Steven Narod, of Toronto University in Canada, as saying.
"It's important to start thinking about action to prevent breast cancer in women at high risk of developing the disease," he added.
The study is published in the British Journal of Cancer.