Fig 1: Immunohistochemical/immunofluorescence expression of Sars-Cov-2 antigens in relation to histopathological changes in thyroid gland obtained from patient who deceased from COVID-19. Sars-Cov-2 spike (S) protein was found notably expressed throughout the thyroid tissue and was localized diffusely in the cytoplasm of follicular cells (A, B, C, D, E, F and J, K, L, M, N, O). Concomitantly, the thyroid gland harboured copious mononuclear infiltrate (A, B, C, D, E, F, G and H) forming granuloma-like structures (B, C, D, E and F) with giant multinuclear cells (arrows on B, D, E, F), epithelial desquamation, colloid depletion and extensive follicular disruption (A, B, C, D, E, F, G, H and I, corresponding to findings consistent with subacute thyroiditis. Spike protein positivity was also found in epithelioid cells within the granulomatous tissue (F). Sars-Cov-2 nucleocapsid protein immunopositivity was noticeably sparser, arranged in punctiform inclusions and localized predominantly in the perinuclear region of follicular cells (arrows on G and H; J, K, L, M, N, O). The majority of remaining follicular cells showed positivity for cleaved caspase-3 (I). Staining was performed using rabbit anti-SARS-CoV-2 spike glycoprotein antibody (Abcam, ab272504; dilution 1:4000), mouse anti-SARS-CoV-2 nucleocapsid protein antibody (Cell Signaling Technology, clone E8R1L; dilution 1:200) and rabbit anti-caspase-3 antibody (Abcam, ab13847; diluted 1:50). Immunoreactions were visualized by DAKO EnVision+System (DAKO Cytomation) for immunohistochemistry or by Alexa Fluor 488 donkey anti-rabbit IgG (Thermo Fisher Scientific; diluted 1:300) and Alexa Fluor 555 goat anti-mouse IgG (Thermo Fisher Scientific; diluted 1:500) secondary antibodies for immunofluorescence studies. Magnifications: A × 100; B, C, D, E, I × 400; F, J, K, L × 600; G, H, M, N, O × 1000.