Breast cancers are made up of different cells
Scientists have discovered a new type of breast tumour.
They believe it might respond to drugs similar to those used to treat prostate cancer.
This is because many of the genes active in the tumour also play a role in producing the male sex hormones that are linked to prostate problems.
The research, by a Swiss team, was presented at the European Breast Cancer Conference in Hamburg, Germany.
The new tumour was discovered during a major European trial comparing two types of chemotherapy.
As part of the study researchers carried out a detailed analysis of the genes which are active in breast tumours.
Dr Pierre Farmer, of the Swiss Institute of Bioinformatics and the Swiss Cancer Research Institute, Lausanne, said: "We have identified a subset of breast tumours that was not previously described by researchers in gene investigation studies."
Previous research has concluded that there were two major groups of tumours based on their cell type, either basal or luminal, plus additional sub-groups based on mutations.
However, the latest study has uncovered a new type of tumour made up of another type of cell called apocrine cells, which are involved in the secretion of milk.
In a small study of 49 tumours, the researchers found that 12% belonged to this new type.
Dr Farmer said many of the genes that were active in the apocrine tumours played a role in the control of male sex hormones called androgens.
Treatment for prostate cancer involves blocking the signals that control androgen production, and Dr Farmer believes a similar strategy may pay dividends if applied to apocrine breast tumours.
He said: "Since inhibition of androgen signalling is an effective strategy to treat prostate cancer, our results raise the possibility that apocrine breast cancer may be treated with anti-androgen drugs."
Dr Farmer warned more work was required before doctors could use the sophisticated methods employed by his team to tailor treatment for individual patients.
However, he said the capacity may become available in the near future.
He said: "Considerable effort is being made to develop biological tools which could help in the future to tailor the treatment to each patient."
Professor Lawrence Young, of Cancer Research UK's Institute of Cancer Studies, said the use of increasingly sophisticated analytical techniques had helped to define sub-sets of particular types of tumour more accurately.
He said: "This holds out the prospect of better diagnosis, and better prognosis, as it may enable us to use therapy more effectively."
Charlotte Augst, of the charity CancerBACUP, said: "This research will hopefully help in the development of more effective treatments for certain types of breast cancer, but it doesn't affect how people with breast cancer are treated at the moment."