Therefore, the goal of this study was to determine the presence of MSI in a cohort of well-defined HNSCC of non-smokers and non-drinkers (NSND).<h4>Methods</h4>Clinical characteristics and tumor tissue of 119 NSND with HNSCC were retrospectively collected and analyzed for MLH1, PMS2, MSH2, and MSH6 protein expression on tissue microarrays (TMA). This evidence concerns the gene MSH6 and head and neck squamous cell carcinoma.