By immunohistochemistry, thyroid angiosarcomas are strongly and diffusely positive for pan-endothelial markers, i.e., CD31 (Fig. 4D), CD34, FLI-1 and ERG, but lack expression of thyroid-related immunomarkers including thyroglobulin, TTF1 and PAX8 [4, 61, 64, 67, 70]. This evidence concerns the gene TTF1 and thyroid gland angiosarcoma.