Breast cancer has not traditionally been considered as an immunogenic disease; however recent studies demonstrate significant associations between immune cell infiltration via tumour infiltrating lymphocytes (TILs) in primary patient breast tumors and clinical outcomes. The presence of TILs has been associated with increased response rates to cytotoxic chemotherapy as well as targeted therapies, leading to improved disease free and overall survival in certain breast cancer subtypes. In this talk I will discuss the clinical significance of TILs, preclinical data suggesting the potential of immunological approaches in breast cancer, as well as recent evidence of objective responses to immunotherapies in breast cancer. As well as this, efforts are ongoing to standardize methodology for evaluating TILs within clinical breast cancer specimens in routine histopathological practice.