XRCC5 and head and neck squamous cell carcinoma: For the NHEJ proteins DNA-PKcs and Ku80, we observed a similar distribution of protein expression across the HNSCC subsites with a clear majority of samples demonstrating strong expression (intermediate staining intensity [2] in >70% or high intensity [3] in >30% of tumor cells), except for the comparably small cohort of oral cavity tumors, in which moderate staining was similarly frequent.