Clinical and morphological characteristics and prognostic significance of the immune microenvironment and the level of PD-L1 expression in squamous cell carcinoma of the tongue and oropharynx

Squamous cell carcinoma of the tongue and oropharynx is characterized by significant clinical and biological heterogeneity, highlighting the need for reliable prognostic and predictive biomarkers. This review analyzes current evidence regarding the significance of programmed death-ligand 1 (PD-L1) expression and immune microenvironment characteristics in these malignancies. PD-L1 has been shown to play a central role in tumor immune evasion; however, its prognostic value remains controversial and appears to depend on human papillomavirus (HPV) status, tumor immune contexture, and methodological approaches used for assessment. More consistent associations with clinical outcomes have been demonstrated for immune infiltration parameters, including high densities of CD8+ T lymphocytes, abundant tumor-infiltrating lymphocytes, and a favorable balance between effector and regulatory immune cells. The combined assessment of PD-L1 expression, immune microenvironment features, and HPV status may improve patient stratification and facilitate personalized treatment strategies. Further studies are required to standardize PD-L1 evaluation methods and to develop integrated prognostic models incorporating molecular and immunological biomarkers.