Chronic Lymphocytic Thyroiditis with Oncocytic Metaplasia Influences PD-L1 Expression in Papillary Thyroid Carcinoma.

Background: Despite the increasing recognition of PD-L1 as predictor of immunotherapeutic response in various malignancies, its role and prognostic significance in thyroid cancer remain underexplored and subject to debate. This study begins to address this gap by comprehensively analyzing PD-L1 expression in papillary thyroid carcinoma (PTC) and investigating its correlation with key clinicopathological variables.

Methods: We conducted immunohistochemistry (IHC) to assess PD-L1 expression in whole-tissue sections from 121 primary papillary thyroid carcinoma (PTC) cases. We then analyzed the correlations between PD-L1 expression and various clinicopathological variables.

Results: PD-L1 expression was detected in 33.1% of papillary thyroid carcinomas (PTCs), predominantly exhibiting weak to moderate intensity. Notably, this study found no significant correlation between PD-L1 expression and various clinicopathological variables. The lack of association with traditional factors such as age, sex, histological subtype, and tumor size suggests the complex and multifaceted nature of PD-L1 regulation in PTC. Multivariate logistic regression analysis identified chronic lymphocytic thyroiditis with oncocytic metaplasia as the sole independent predictor of PD-L1 expression (P = 0.014), underlining the potential influence of the tumor microenvironment on immune checkpoint expression in PTC.

Conclusions: Our study underscores the intricate interplay between chronic lymphocytic thyroiditis with oncocytic metaplasia and PD-L1 expression in papillary thyroid carcinoma. The observed link suggests a potential avenue for therapeutic intervention using anti-PD-1/PD-L1 therapies in surgery-refractory PTC. Understanding the dynamics of immune checkpoint regulation in the context of the tumor microenvironment is crucial for devising effective treatment strategies. Future research endeavors should delve deeper into the molecular mechanisms underlying this interaction and explore its implications for patient outcomes. As the field of immunotherapy continues to evolve, our findings contribute valuable insights into the complex immunological landscape of thyroid cancer.