Scientists have created a genetic 'map' of breast cancer
A genetic "map" of breast cancer has been drawn, revealing the varied landscape of the disease in more detail than ever before.
The research is expected to lead to more accurate diagnoses and effective treatments.
Scientists described nine new genes that drive the development of breast cancer, bringing the known total to 40.
Breast cancer was shown to be not so much a single disease as a diverse range of cancer "species". Most individual cancers had different combinations of mutated cancer genes.
The research, conducted by a large international team of British-led experts, involved analysing DNA from 100 tumour samples. Scientists scoured more than 21,000 genes for cancer-causing "driver" mutations that can turn an ordinary cell into one that multiplies uncontrollably.
They also identified nine genes previously not known to be linked to the disease.
Study leader Professor Mike Stratton, director of the Wellcome Trust Sanger Institute in Hinxton, Cambridgeshire, said: "In 28 cases we found only a single driver, but the maximum number of driver mutations in an individual cancer was six. We found that breast cancer can be caused by more than 70 different combinations of mutations.
"If we consider three breast cancers, each with four driver mutations: they might share none of those driver mutations - so each is a different genetic 'animal'. They are different cancers driven by different genes. We need to classify them as carefully as we can. This study is a step towards that goal."
All cancers carry mutations - changes in the genetic code - that are acquired during a person's lifetime. A subset of these, known as driver mutations, are causally related to the development of cancer. Others, called "passenger" mutations, may be present without directly triggering the disease.
The new research, published in the journal Nature, involved the first comprehensive exploration of breast cancer driver mutations. Scientists hope their findings will ultimately lead to new and better treatments, tailored to the genetic make-up of individual patients.