Development and progression of malignant tumors are characterized by a constant interaction of tumor cells in tumor microenvironment with infiltrating immune cells. In the early stage human epidermal growth factor (HER2) positive and in triple negative breast cancer (TNBC), immune infiltrates are detectable in up to 75% of tumors, with up to 20% of tumors having a particularly dense infiltrate and with lower amount of Tumor-infiltrating lymphocytes in luminal subtypes. Tumor-infiltrating lymphocytes (TILS) reflect the attempt of the host to eradicate malignancies, and over the past years, they have been shown to possess a promising prognostic value for breast cancer, particularly in case of HER2 positive and triple-negative molecular subtypes. In parallel, the clinical evaluation of TILs has been shown to effectively predict treatment outcomes in both neo/adjuvant settings. Currently, tumor-infiltrating lymphocytes are promising further predictive utility in the era of novel immune-related therapeutic options which are coming into the clinical setting launching a solid rationale for the future treatment options.
In this review article we are going to highlight the basics and recent studies the field of interactions between immune response and breast cancer.