Triple negative breast cancer is defined by the absence of estrogen receptors, progesterone receptors, and HER2 overexpression. This means common targeted therapies such as hormone blockers and HER2 inhibitors are ineffective, so treatment relies mainly on surgery, chemotherapy, and radiotherapy. It often affects younger women, can grow quickly, and has a higher risk of early recurrence and metastasis, especially to brain and lungs.

Research shows that triple negative breast cancer is highly heterogeneous. Genomic studies reveal multiple subtypes with distinct patterns of gene expression, mutations, and immune activity. Some subtypes show defects in DNA repair pathways, particularly involving BRCA1 and BRCA2, making them sensitive to platinum-based chemotherapy and PARP inhibitors that exploit these repair weaknesses.

The tumor microenvironment is another major focus. Many triple negative tumors are infiltrated by immune cells, and higher levels of tumor infiltrating lymphocytes are associated with better prognosis and improved response to chemotherapy. This has led to the development of immunotherapies such as checkpoint inhibitors targeting PD 1 or PD L1. Clinical trials indicate that adding these agents to chemotherapy can improve outcomes in selected patients, particularly those whose tumors express PD L1 or have strong immune infiltration.

Researchers are also investigating androgen receptor targeting, antibody drug conjugates that deliver toxic drugs directly to cancer cells, and strategies to overcome chemotherapy resistance. Overall, the field is moving from viewing triple negative breast cancer as a single entity toward a set of biologically distinct diseases, enabling more personalized and effective treatments.