A discovery compared with “finding gold” has identified three genes linked to hormonal breast cancer.

After decades of research, the new genes have been found to influence the oestrogen receptor gene, which is the main driver of hormonal breast cancer.

Four out of five breast tumours occur after biochemical changes are triggered when the female hormone oestrogen binds to this receptor molecule on cells.

Professor Mitch Dowsett, who led the scientists at the Institute of Cancer Research in London, said: “This research is exciting because it shows that while the oestrogen receptor is the main driver of hormonal breast cancer, there are others next door to it that also appear to influence breast cancer behaviour.”

Dr Anita Dunbier, one of the Breakthrough Breast Cancer researchers, said:

“This is a surprising discovery. We found these genes in a place we thought we knew a lot about – it is like finding gold in Trafalgar Square.

The findings could lead to new ways of diagnosing and treating the most common form of breast cancer.

 “We now have to look further at how these genes work, but the discovery could lead to possible new therapies that will benefit women with breast cancer in the future,” said Dr Dunbier.

The genes’ activity is unlikely to be affected by current treatments such as tamoxifen which target the oestrogen receptor. This means they could be potential targets for new drug treatments.