Abstract: Triple- negative breast cancer (TNBC) is defined by the lack of estrogen receptors (ERs) and progesterone receptors (PRs) and by the human epidermal growth factor receptor 2 (HER 2)-negative status. TNBC accounts for 15% to 20% of breast cancer cases. Genomic profiling studies have demonstrated that breast cancer heterogeneity extends beyond the classic immunohistochemistry (IHC)- based divisions. TNBC is also a heterogeneous disease on the molecular level, as well as on the pathologic and clinical levels. Thus, the molecular subclassification of TNBC will be of considerable value to the development of targeted therapies. However, no widely recognized standard for the molecular classification of TNBC exists. This review provides a brief summary on the latest research on TNBC.