Patho-biological aspects of basal-like breast cancer

Breast cancer comprises a remarkably diverse group of diseases in terms of presentation, morphology, molecular profile and response to therapy. Recent gene expression profiling of breast cancer has identified specific molecular subtypes of clinical significance. Basal-like cancers (BLC) comprise a group of tumours that are characterised by an expression signature similar to that of the basal/myoepithelial cells of the breast and cluster together with BRCA1 associated tumours. Although BLC has fascinated oncologists and scientists alike due to its enigmatic clinical and pathological parameters, there is no consensus about the definition and method of identification in routine practice of this rather heterogeneous group of cancers. Furthermore, the prognostic significance of BLCs and response to specific chemotherapy regimens are still a matter debate. In this review, we discuss the molecular and morphological features, prognostic significance of BLC, and explore its impact on the concept of the breast cancer stem cell.