Introduction:Head and neck squamous cell carcinoma(HNSCC)is a common cancer worldwide and has a poor prognosis.A biomarker predicting the clinical outcome of HNSCC patients could be useful in guiding treatment planning.Overexpression of the T lymphoma invasion and metastasis 1(Tiam1) protein has been implicated in the migration and invasion of neoplasms.However,its role in HNSCC progression needs to be further validated.We detected the expression of Tiam1 in normal and tumor tissues and determined its association with clinical outcomes in patients with HNSCC.Methods:We measured the expression ofTiam1 in normal and cancerous tissue samples from the patients with HNSCC treated at Sun Yat-sen University Cancer Center between 2001 and 2008.The Tiam1 expression was scored from 0 to 12 based on the percentage of positively stained cells and the staining intensity.We then determined the diagnostic performance of this score in predicting overall survival(OS) and disease-free survival(DFS).Results:Of the 194 evaluable patients,those with advanced disease,lymph node metastasis at diagnosis,and recurrence or metastasis during follow-up had a higher tendency of having high Tiam1 expression as compared with their counterparts(P<0.05).The proportion of samples with high Tiam1 expression was also higher in cancerous tissues than in non-cancerous tissues(57.7%vs.13.9%,P<0.001).Cox proportional hazards regression analysis revealed that Tiaml expression scores of 5 and greater independently predicted short OS and DFS.Conclusion:The Tiaml expression is shown as a promising biomarker of clinical outcomes in patients with HNSCC and should be evaluated in prospective trials. A biomarker predicting the clinical outcome of HNSCC patients could be useful in guiding treatment planning. Overexpression of the T lymphoma invasion and metastasis 1 (Tiam1 ) has been implicated in the migration and invasion of neoplasms. However, its role in HNSCC progression needs to be further validated. We detected the expression of Tiam1 in normal and tumor tissues and determined its association with clinical outcomes in patients with HNSCC. Methods : We measured the expression of Tiam1 in normal and cancerous tissue samples from the patients with HNSCC treated at Sun Yat-sen University Cancer Center between 2001 and 2008. Tiam1 expression was scored from 0 to 12 based on the percentage of positively stained cells and the staining intensity. We then determined the diagnostic performance of this score in predicting overall survival (OS) and disease-free survival (DFS) .Resu lts: Of the 194 evaluable patients, those with advanced disease, lymph node metastasis at diagnosis, and recurrence or metastasis during follow-up had a higher tendency of having high tiam1 expression as compared with their counterparts (P <0.05). proportion of samples with high Tiam1 expression was also higher in cancerous tissues than in non-cancerous tissues (57.7% vs.13.9%, P <0.001) .Cox proportional hazards regression analysis revealed that Tiaml expression scores of 5 and more likely regulated short OS and DFS . Conlusion: The Tiaml expression is shown as a promising biomarker of clinical outcomes in patients with HNSCC and should be evaluated in prospective trials.