Fig. 2

Photomicrographs showing histological and immunohistochemical findings in tumor tissue. a Intraoperative frozen section of the tumor tissue. Polygonal cells proliferated in nests and cords. Many blood vessels (arrows) were found between the nests and cords. Hematoxylin and eosin staining in the formalin-fixed paraffin-embedded tumor tissue showed numerous thin-walled microvessels (b) and proliferation of vacuolated atypical sheeted tumor cells with clear and eosinophilic cytoplasm (c). d A small part of the tumor had a thyroid follicle-like pattern including eosinophilic liquid. CD31 (e) and CD34 (f) staining were positive. g The tumor was diffusely positive for vimentin. h Thyroid transcription factor-1 (TTF-1)-positive cells were present in part of the tumor. a, b, e–h ×200; c, d ×600