J. Lachapelle* and WD Foulkes† of BRCA1 somatic mutations, studies suggest that the BRCA1 pathway may be dysfunctional in at least some nonhereditary basal-like tumours. It is now clear that both the basal-like and the triple-negative breast cancers are heterogeneous subgroups that will probably be more precisely defined in the future 4, 5. Nevertheless, the actual definitions of basal-like and triple-negative breast cancer have been demonstrated to be clinically significant, in that they identify breast cancer patients with different risk factors and, importantly, different natural histories 4, 6. Women who develop a basal-like breast cancer are more likely to have reached menarche at a younger age, to have had a higher body mass index during their premenopausal years, and to have had a higher parity and lower lifetime duration of breastfeeding in comparison with women without cancer 7. The basal-like and triple-negative phenotypes are both associated with usually aggressive high-grade invasive

Since the start of the 1990s, molecular pathology has been playing an increasingly important role in cancer diagnosis and treatment. Nowhere is this role more evident than in the case of breast cancer. Traditional criteria such as the size and histologic grade of the primary tumour and the number of positive axillary lymph nodes have been the major focus for many years. Today, immunohistochemical tests and other molecular and cytogenetic tests are usually necessary for an exact diagnosis and for assessment of the degree of invasiveness. Moreover, those tests are now essential for an accurate evaluation of prognosis and initiation of the appropriate treatment. Since 2000, hypothesis-free gene-expression studies of breast cancer have identified 5 different “intrinsic” molecular subtypes having prognostic value, initially defined as luminal A, luminal B, HER2 (human epidermal growth factor receptor 2)–