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

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. 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. 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). 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.