CD274 and Hashimoto thyroiditis: Indicatively, Lubin et al. revealed that PD-L1 was upregulated not only in PTC cells but also in non-neoplastic follicular epithelium in the background of Hashimoto’s thyroiditis, suggesting an adaptive immune response, in which PD-L1-negative follicular cells are eliminated by the autoimmune infiltrate, leaving behind a PD-L1-enriched cell population [28].