Background Programmed cell death protein 1 (PD‐1) is an immune checkpoint receptor which plays an important role in a patient´s immune responses to microbial and cancer antigens. It is expressed in tumor infiltrating lymphocytes (TILs) with many different malignancies. The aim of the study was to evaluate PD‐1 expression and its prognostic value in tongue cancer.

Methods The data of tongue squamous cell carcinoma (TSCC) patients (N=81) treated in Tampere University Hospital between 1999‐2013 was used. Control data consisted of patients with non‐malignant tongue mucous membrane lesions (N=48). The formalin‐fixed paraffin‐embedded samples were stained immunohistochemically and scanned via digital microscope. The staining of PD‐1 was examined semi‐quantitatively.

Results The density and intensity of PD‐1+ cells were significantly higher in TSCC than in control samples. The expression of PD‐1 correlated with better survival.

Conclusions The expression of PD‐1 could be a potential prognostic marker in TSCC. Further research using larger sample size is needed.