Basal-like and triple-negative breast cancers: searching for positives among many negatives.

Triple-negative breast cancers (TNBC) are defined by their failure to express the estrogen receptor, progesterone receptor, and HER2/neu protein markers. This basic feature is clinically relevant because it indicates that these cancers cannot be managed with endocrine or anti-HER2 systemic therapies. Furthermore, most TNBC cases are also characterized as being of the genetically defined basal subtype, which is an inherently and biologically more aggressive pattern of disease. The two terms, however, are not synonymous, and some TNBC cases are prognostically more favorable. TNBC differs from non-TNBC in risk-factor profile, pattern, and rate of metastatic spread.