Basal-like Breast Cancer—Characteristics, Risks, and Associations

Breast cancer is a heterogeneous disease. Gene expression profiling has demonstrated the existence of at least five ‘intrinsic’ subtypes: luminal A, luminal B, human epidermal growth factor-2 receptor (HER2), normal-like, and basal-like. While the estrogen receptor (ER), progesterone receptor (PR), and HER2 remain the most important prognostic markers and predictors of response to therapy, interrogating thousands of genetic transcripts more accurately captures the biological complexity and clinical heterogeneity of this disease. Target identification through massively parallel sequencing is likely to bear fruit in the coming years. Attention to basal-like breast cancers has grown substantially due to their generally poor prognosis, lack of targeted therapies, and connection with BRCA1 -related cancers. In this article, we discuss the basal-like subgroup with respect to its cellular origins, relationship to BRCA1 , and associated epidemiological risk factors.