Overexpression of MLH1 is associated with tumour location (p=0.002) and tumour invasive depth (p=0.045); high expression of MPG is associated with tumour location (p=0.014), lymphatic invasion (p=0.006) and TNM stage (p=0.008); overexpression of Polβ is associated with perineural invasion (p=0.043) and advanced TNM staging (p=0.008); XRCC1 overexpression is associated with histology (p=0.044) and presence of lymphatic invasion (p=0.005); while FEN1 protein expression did not present any significant association with clinical data. The gene discussed is MPG; the disease is neoplasm.