Updates on Molecular Classification of Triple Negative Breast Cancer

Purpose of Review: Clinical management of triple negative breast cancer (TNBC) is challenging as patients have heterogeneous responses to systemic therapy, and there is no established therapeutic target. Gene expression profiling and genomic sequencing analysis are among the first steps in understanding the biology of TNBC. In this paper, we review the molecular classification of TNBC and discuss the implications for systemic therapy. Recent Findings: Clonal and mutational spectrum analyses of TNBC show that it is highly heterogeneous with a diverse mutational pattern and can be clustered into different subtypes including basal-like, luminal androgen receptor, and mesenchymal, based on gene expression profiling. Although knowledge of these subtypes is not used in routine clinical practice, studies have shown that patient outcomes differ according to subtype, with higher pathological complete response rates to chemotherapy reported in basal-like subtypes. Clinical trials with targeted agents are now starting to incorporate molecular subtypes into eligibility criteria. Summary: TNBC is molecular heterogeneous, and therefore, a wide spectrum of patients’ clinical outcomes exists. Incorporating molecular subtypes into treatment algorithms may offer clinicians greater precision in managing TNBC patients.