Primary tumors and metastatic lesions of head and neck squamous cell carcinoma patients show distinct tumor immune cell microenvironments

Introduction Head and neck squamous cell carcinoma (HNSCC) are a heterogenous tumor entity, located in oropharynx (OPSCC), oral cavity, larynx and hypopharynx with a different biological behavior of distant and nodal metastasis. Inspite of a high initial treatment response, nearly 50 percent of HNSCC show locoregional recurrence. Immune cell infiltration of tumor microenvironment (TME) in HNSCC affects clinical outcome and offers multiple treatment targets as PD-L1.