[Research progress of tumor infiltrating lymphocytes in breast cancer]

Breast cancer is a heterogeneous disease. The formation and progression of tumor and the sensitivity to treatment differs from patient to patient. In addition to the widely used molecular subtype, novel markers are needed to better personalize the treatment of breast cancer. Tumor infiltrating lymphocyte (TIL) have been consistently documented in breast cancer lesions especially in triple negative and human epidermal growth factor receptor-2 positive breast cancer. Several clinical trials have revealed that TIL are associated with prognosis and can predict therapeutic efficacy of special therapy. TIL could be divided to different subtypes including CD8 + TIL, CD4 + TIL, cytotoxic T lymphocyte-associated antigen-4 + TIL, programmed death-1 + TIL. They play different roles in the process of anti-tumor immunity and can predict different prognosis. Screening out special TIL subtype which is well associated with prognosis and therapeutic efficacy and developing targeting immunotherapy can help to improve outcomes of breast cancer patients.