CD274 and Hashimoto thyroiditis: In accord with previous reports [32–34], we also observed an increased expression of PD-L1 expression in chronic lymphocytic thyroiditis and Hashimoto's thyroiditis, suggesting that the chronic inflammation might provide a microenvironment enriched with different cytokines such as IFNγ, IL-1, IL-10, IL-6 that could trigger upregulation of PD-L1 expression.