What we currently call breast cancer should be thought of as 10 completely separate diseases, according to an international study which has been described as a "landmark".
The categories could improve treatment by tailoring drugs for a patient's exact type of breast cancer and help predict survival more accurately. The study in Nature analysed breast cancers from 2,000 women.
It will take at least three years for the findings to be used in hospitals.
Researchers compared breast cancer to a map of the world. They said tests currently used in hospitals were quite broad, splitting breast cancer up into the equivalent of continents.
The latest findings give the breast cancer map far more detail, allowing you to find individual "countries". "Breast cancer is not one disease, but 10 different diseases," said lead researcher Prof Carlos Caldas.
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