Triple-Negative Metastatic Breast Cancer

This chapter provides answers to practice-based questions with case studies covering the new principles of diagnosis, classification, staging, treatment, and outcomes in the rapidly advancing field of triple-negative metastatic breast cancer. TNBC is a subtype of breast cancer that accounts for approximately 15% of all breast cancer cases as per national population-based studies. TNBC is more frequently seen in younger patients compared with other types of breast cancer. It mostly presents in young premenopausal women and has a predilection for development in African American women. From a pathologic standpoint, this subtype is characterized by the lack of expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Chemotherapy continues to be the main treatment approach, although recent successes have been achieved owing to the incorporation of immunotherapy and/or targeting of DNA damage pathways in appropriate cases.