[Lynch syndrome: What is new?]

Lynch syndrome is a genetic condition defined by a germline mutation of an MMR (MisMatch Repair) gene leading to a defective DNA MMR system. Therefore, it is characterized by the predisposition to a spectrum of cancers, primarily colorectal cancer (CRC) and endometrial cancer (EC). Lynch syndrome-related CRC accounts for 3% of all CRC. Lynch syndrome also accounts for 2% of all EC. In case of Lynch syndrome, there is usually a familial history of cancer defined by the Amsterdam and Bethesda criteria. Diagnosis is made by tumor testing with (i) MMR immunohistochemistry and (ii) PCR for MSI (microsatellite instability), a genetic phenotype that characterizes these tumors. MSI can also be detected in sporadic tumors, through epigenetic events inactivating the MMR system. Progress in diagnosis and molecular biology has allowed for better identification of Lynch patients but also other rare genetic syndromes. MSI tumors can now benefit from new treatments such as immunotherapy which underlines the importance of their diagnosis. Finally, patients with Lynch syndrome as well as their relatives, undergo specific surveillance in order to prevent development of other cancers. This review will summarize the different aspects of Lynch syndrome and also focus on recent progress on the topic.