Study of PD-L1 Expression in Papillary Thyroid Carcinoma and Its Correlation to the Clinicopathologic Characteristics

Abstract Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, generally associated with a favorable prognosis. Programmed death-ligand 1 (PD-L1), an immune checkpoint protein, has been implicated in tumor immune evasion and is emerging as a potential prognostic marker in PTC. The study aimed to assess PD-L1 expression in patients with PTC and also to determine its correlation with clinicopathologic parameters. This is a cross-sectional study conducted to assess the PD-L1 status by immunohistochemistry on formalin-fixed and paraffin-embedded surgical tissues of 50 patients diagnosed with PTC and its variants in the period from 2020 to 2022. The clinicopathologic features were studied and correlated with the PD-L1 status. PD-L1–positive expression was detected in 16/50 patients (32%) at a 1% threshold. In our study, a statistically significant correlation was found between patients with PD-L1–positive tumor cells and higher T stage (p = 0.021), and positive pathological lymph nodes (LNs) (p = 0.01). All the 16 patients who were found to have PD-L1–positive expression received radioactive iodine treatment (p = 0.034), whereas no association was found with age (p = 0.197), sex (p = 0.584), multifocality (p = 0.566), lymphovascular invasion (p = 0.061), extrathyroid extension (p = 0.725), thyroiditis (p = 0.135), histological variants (p = 0.520), margins (p = 0.410), and postoperative thyroglobulin (p = 0.120). PD-L1 expression correlates with T stage and pathological LNs and may be used as a prognostic marker for patients with PTC. Further follow-up needs to be done to confirm the prognostic value of PD-L1 expression in PTC.