Immunoexpression of hMSH2 and hMLH1 in oral squamous cell carcinoma and its relationship to histological grades of malignancy

BACKGROUND: The aim of this study was to describe the human mutS homolog 2 (hMSH2) and human mutL homolog 1 (hMLH1) immunoexpression in different areas of oral squamous cell carcinoma (OSCC) - central/superficial (C/S) and invasive tumor front (ITF) - in an attempt to verify if the histological grade of malignancy interferes in this expression. METHODS: Forty-six samples of OSCC were analyzed histologically. Twenty-six cases (56.5%) presented ITF. Histological grades of malignancy were evaluated in all samples, and immunohistochemistry was applied using specific antibodies against hMSH2 and hMLH1 proteins. Immunoexpression was semiquantitatively scored, and results were correlated with their histological grades of malignancy. RESULTS: The hMSH2 immunoexpression in both C/S and ITF was not correlated with histological grades of malignancy, whereas hMLH1 overexpression was correlated (P = 0.043) and associated (P = 0.041) with well-differentiated tumors. In addition, hMHL1 reduction or negative expression was detected in poorly differentiated tumors. Moreover, negative expression for hMSH2 and hMLH1 proteins was demonstrated in some cases of OSCC. CONCLUSIONS: The findings of the present study indicate that the histological grade of malignancy interferes in hMLH1 immunoexpression. The negativity for both hMSH2 and hMLH1 proteins in some cases suggests a possible association between OSCC and hereditary non-polyposis colorectal cancer. Further investigation from future studies is needed to elucidate this supposition.