CD274 and Hashimoto thyroiditis: A significant association was also identified between PD-L1 expression and coexisting Hashimoto’s thyroiditis, in line with findings from previous studies and confirmed by meta-analyses [12,13,20,22,23,25,27,28]. PD-L1 expression has also been observed in Hashimoto’s thyroiditis in the absence of PTC, supporting the notion that autoimmune inflammation may independently drive PD-L1 upregulation.