Do 'basal-like' breast cancers really exist?

It has been proposed that gene expression profiles will revolutionize the classification of breast cancer, eventually replacing histopathology with a more reproducible technology. These new approaches, combined with a better understanding of the cellular origins of breast cancer, should enable us to identify patient subgroups for more effective therapy. However, in such a rapidly advancing field it is essential that initial and thought-provoking results do not become established as 'facts' without question. This Opinion addresses some of the negatives and positives generated by the term 'basal-like' breast cancer, and questions its existence as an entity.