Fig. 1

a, Papillary thyroid carcinoma (PTC) with predominant papillary structures; b, The background thyroid tissue of (a), which showed dense lymphoplasmacytic infiltrates and germinal center formation indicating the presence of chronic lymphocytic thyroiditis; c, PD-L1 was diffusely expressed both on the cell membrane and the cytoplasm. Please note there was also staining on the tumor-infiltrating lymphocytes (TILs), which should not be regarded as positive staining of the tumor cells; d, PD-L1 was focally expressed on the tumor cell membrane; e, PD-1 expression of the TILs was identified in the tumor stroma; f, PD-1 expression was noted in the tumor invasive front; g, BRAF V600E was strongly and diffusely expressed on the tumor cytoplasm; h, Mild but diffuse expression of BRAF V600E was noted on the PTC