الفهرس 
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Abstract
Introduction: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. Recently, the novel immunotherapies bring promising clinical advances in treatment of cancers. One of most important target for cancer immunotherapy is PD-L1. Many human cancers display PD-L1 over-expression. There are few studies about the expression of PD-L1 in HNSCC, meanwhile these existing studies have shown conflicting results about the positive expression rate of PD-L1 and its relation with clinicopathological factors.
In recent decades, studies in several cancers recognize tumor budding as a sign of invasion and metastasis. Tumor budding is the presence of small clusters of less than five cancer cells outside the main part of the tumor. Presence of tumor budding has been correlated with lymph node metastasis, recurrence and decreased survival. In