Abstract
Triple negative breast cancer (TNBC) is a subtype of breast cancer which does not express or expresses a minimum amount of estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor receptor 2 (HER2) protein. TNBCs include a heterogenic group of cancers that are aggressive, grow rapidly and are associated with poor prognosis and overall survival, mainly attributed to a lack of effective therapeutic targets. For a long time, a major issue with predicting the outcome and prognosis of TNBCs was the lack of an accurate biomarker, a molecule that helps us objectively assess a patient's health status. In recent times, defining the presence of tumor-infiltrating lymphocytes (TIL) is becoming an indispensable method of determining a patient's prognosis. TILs are found in tumor tissue and the surrounding stroma and carry a prognostic value. Furthermore, they are known to improve the effect of systemic therapy. With the rise of immunotherapy, the role of TIL in this newer therapeutic option is a topic of increased importance. The goal behind this research article is a comprehensive review of the current literature on the importance of tumor-infiltrating lymphocytes in the prognosis of TNBC.