Triple-Negative Breast Cancer: One Or More Entities?

Characterized by an aggressive clinical course and relatively poor prognosis, triple-negative breast cancer (TNBC) refers to a diverse group of tumors with distinct molecular characteristics rather than to a single entity. The recognition of distinct gene expression subtypes within the group of TNBC and the description of an ever-expanding set of genetic events has led to improved understanding of the underlying biology. However, the improvement of clinical results has been incremental despite undergoing efforts to evaluate the role of molecularly targeted agents in the treatment of TNBC. The relative rarity of each one of these genetic events increases the difficulty of conducting large clinical trials, further hindering our ability to identify meaningful, personalized treatment approaches. Herein, we summarize current knowledge on TNBC, focusing on molecular pathology and emerging treatment approaches.