Predictive relevance of programmed cell death protein 1 and tumor-infiltrating lymphocyte expression in papillary thyroid cancer

Background: Co-signaling molecule programmed cell death 1 ligand 1 has been shown to induce potent inhibition of T cell-mediated antitumoral immunity. Our study aimed to investigate the prognostic value of programmed cell death 1 ligand 1 expression and tumor-infiltrating lymphocyte density as biomarkers in specimens from patients with papillary thyroid cancer. Methods: We retrospectively analyzed the data and tissue samples of 75 patients with papillary thyroid cancer. Stained cells were counted manually and analyzed for clinical and histopathologic correlations and disease-free survival. Results: Programmed cell death 1 ligand 1 expression was significantly correlated with increased incidence of lymphovascular invasion (P = .038), extrathyroidal extension (P = .026), and concurrent lymphocytic thyroiditis (P = .003). Patients with low CD8+ and CD3+ expression presented with a significantly higher incidence of lymph node metastasis (P = .042) and extrathyroidal extension (P = .015). The subgroup of cases with positive programmed cell death 1 ligand 1 expression and low CD8+ T cell infiltration demonstrated a significantly increased incidence of lymph node metastasis (P = .031). Univariate and multivariate analysis confirmed that a high CD8+ T cell density was significantly associated with favorable disease-free survival (P = .017). Subanalysis revealed that the shortest disease-free survival was evident in the programmed cell death 1 ligand 1+/CD8low group (P = .004). Conclusion: Our findings indicate that CD8+ tumor-infiltrating lymphocyte density and programmed cell death 1 ligand 1 expression may serve as valuable predictive biomarkers in patients with papillary thyroid cancer.