PD-L1 expression in head and neck cancer – Variability, prognostic value and therapeutic relevance

Introduction The PD-L1-related immune escape of head and neck tumor cells is known as a mechanism of tumor proliferation, but the increased expression of PD-L1 in the tumor appears to be a prognostic factor dependent on the tumor entity. Accordingly, the relevance of PD-L1 in head and neck squamous cell carcinoma (HNSCC) has not been clearly clarified. In particular, the question of the homogeneity of the marker within the tumor and in the comparison of tumor and metastasis arises.