Tumor infiltrating lymphocytes in early breast cancer

Immunoediting represents a complex and dynamic process involving cancer and immune system cells, composed by three intertwined phases: elimination, equilibrium and escape. A large number of immune cell subtypes are involved, each playing a peculiar role in interacting with cancer cells: cytotoxic CD8(+) T cells play a main role in cancer killing by inducing tumor cell death, while FOXP3(+) T-regulatory cells represent an immune-inhibitory cell subtype. The evaluation of tumor infiltrating lymphocytes (TILs) in H&E routine samples has been shown to represent a reliable surrogate of the immune anti-tumor activity and a robust independent prognostic biomarker in breast cancer (BC) patients, especially in the Tripe Negative and HER2thorn subtypes. The present review addresses the mechanisms of breast cancer immunoediting, its cell complexity and prognostic/predictive relevance, providing evidence that TILs represent one the most promising biomarkers for BC patients.