MLH1 and head and neck squamous cell carcinoma: A Canadian study was instead able to find a significant correlation between HNSCC and the presence of MSI, but not with MMR proteins dysfunction: investigating MSI status and hMLH1 and hMSH2 expression among 24 young HNSCC patients (≤44 years old; 46% smokers) and comparing it with an older cohort (33 HNSCC cases, ≥45 years, 88% with a history of tobacco abuse), they found that 100% of tumors in the younger cohort were MSI+ at least at one site, while 61% MSI+ tumors were found among the older patients [38].