MLH1 and neoplasm: 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).