The latest breast cancer research could lead to more personalised care for patients and help further understanding of the causes of the disease, scientists said.
A study involving people from around the world has been hailed as giving a more complete picture of the changes in DNA in breast cancer, providing potential opportunities for new treatments.
A study of 560 breast cancer genomes, or complete genetic codes, turned up five new genes associated with the disease.
The results, published in Nature and Nature Communications, provide evidence that breast cancer genomes are "highly individual", researchers from the Wellcome Trust Sanger Institute said.
The team looked at genomes in patients, four of whom were men, and focused on mutations that encourage the disease to grow and the patterns - known as mutational signatures - in each tumour.
They found that women with genes that leave them at a higher risk of developing breast and ovarian cancer, have entire genome profiles that are very different to each other and distinctive from other breast cancers.
Dr Serena Nik-Zainal, who led the team of researchers, said: "In the future, we'd like to be able to profile individual cancer genomes so that we can identify the treatment most likely to be successful for a woman or man diagnosed with breast cancer. It is a step closer to personalised healthcare for cancer."
Dr Ewan Birney, from the European Bioinformatics Institute, analysed the sequence of genetic information in the sample genomes.
He said: "This study both gave us the first large scale view of the rest of the genome, uncovering some new reasons why breast cancer arises, and gave us an unexpected way to characterise the types of mutations that happen in certain breast cancers."
Professor Sir Mike Stratton, director of the Wellcome Trust Sanger Institute, said discovering gene mutations is "crucial" to understanding the causes of cancer and coming up with better treatments.
He said: "This huge study, examining in great detail the many thousands of mutations present in each of the genomes of 560 cases brings us much closer to a complete description of the changes in DNA in breast cancer and thus to a comprehensive understanding of the causes of the disease and the opportunities for new treatments."