TG and Hashimoto thyroiditis: Serum of a Hashimoto thyroiditis patient served as positive control, showing both granular staining in the cytoplasm of the follicle epithelium (Figure 3B, white arrowheads) and coarse staining in the colloid of follicles (Figure 3B, white asterisk), which represented anti-TPO and anti-TG seropositivity, respectively.