Here at Prevent Breast Cancer, we use the idea of a spectrum when we talk about breast cancer risk, rather than quoting numbers such as 1 in 9, 1 in 8 etc. This is because we believe these numbers are in fact a bit misleading.
At one end of the scale, there are women who carry a very high-risk gene such as BRCA1 or BRCA2, whose risk can be as high as 85%. At the other end of the scale are women who, as a result of their genetics and lifestyle have only a very low risk of around 1 in 50.
Most women are somewhere in the middle. For the average woman, who does not carry a high-risk gene, the risk is probably around 1 in 20.