What is triple-negative breast cancer?

Triple-negative (ER-negative, PR-negative, HER2/neu not overexpressed) breast cancer has distinct clinical and pathologic features, and is a clinical problem because of its relatively poor prognosis, aggressive behaviour and lack of targeted therapies, leaving chemotherapy as the mainstay of treatment. Most triple-negative tumours fall into the basal-like molecular subtype of breast cancer, but the terms are not completely synonymous. Among the intriguing characteristics of triple-negative breast cancer is its association with cancers arising in BRCA1 mutation carriers, in young women and in African–American women. The reasons for these associations are unclear but may ultimately provide avenues for prevention and targeted therapy. This review discusses the definitions and characteristics of as well as current and evolving therapies for triple-negative and basal-like breast cancer.