[Evaluation of tumor-infiltrating lymphocytes in breast cancer: How to use the 2014 international guidelines?]

With the major development of immunotherapies, evaluation of the immune response associated to cancer has become the new challenge for pathologists. In breast cancer, this perspective has been notably anticipated by the recent publication, in 2014, of international guidelines for assessment of tumor-infiltrating lymphocytes (TILs), on routine haematoxylin-eosin stains. This technical article aims at reviewing the main key points and different steps in evaluation of tumor-infiltrating lymphocytes, in order to allow an easy implementation of this putative biomarker in routine practice. Widespread diffusion of international guidelines is the key to development of a standardized and reproducible biomarker. This early learning phase is of particular importance, as immune response will probably play a major role as a prognostic and predictive biomarker, especially in triple-negative and HER2 positive breast cancer.
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