Abstract: Objective To detect the expression levels of SMAD4 in Tongue Squamous Cell Carcinoma (TSCC) and analyze its correlation with cellular differentiation degree and lymph node metastasis. Methods 8 cases of normal oral mucosa paraffin specimens, 38 cases of TSCC paraffin specimens were collected in the present experiment. Immunohistochemical staining was used to detect the expression levels of SMAD4 in normal and TSCC tissues. Results SMAD4 protein in squamous cell carcinoma tissues showed lower expression level than in normal tongue mucosa tissues(P <0.05). Well differentiated TSCC and moderately or poorly differentiated TSCC had no significant difference in overall expression levels of SMAD4 protein（P＞0.05）. But the SMAD4 expression in nuclei of the cells in well differentiated TSCC group was higher than that in moderately or poorly differentiated TSCC group（P＜0.05）. SMAD4 expression in nuclei of the cells in non- metastatic TSCC group was higher than that in metastatic TSCC, especially in moderately or poorly differentiated TSCC group (P <0.05). Conclusion The expression level of SMAD4 in TSCC , especially in nuclei of the cells correlates with differentiation levels of TSCC cells and tumor metastasis.

Key words: SMAD4, squamous cell carcinoma, metastasis