We report the case of a patient with a metastatic chemoresistant sarcoma. Considering the few therapeutic options, we performed an extensive sequencing of the tumor and leucocytes DNA. We identified a constitutional mutation in the MLH1 gene which was not expected considering the family history. Because of this mutation affecting genome stability, we expected that the tumor cells would be a good candidate for immune therapy with checkpoint inhibitors. we administrated an anti PD-1 antibody to the patient who achieved a complete tumor response. This observation underlines the overlap between tumoral and germline genetics and emphasizes the impact of genomic medicine for guiding treatment decision. (By Dr. Camille Tlemsani, https://jmg.bmj.com/content/early/2018/10/23/jmedgenet-2018-105594 )