Fig. 3

Macroscopic and histological findings. a Cut surface of the thyroid tumor (bar, 10 mm). b The tumor invaded the surrounding thyroid tissue. Hematoxylin and eosin staining (bar, 200 μm). c The tumor exhibited various growth pattern; follicular, solid, and papillary (hematoxylin and eosin; bar, 200 μm). d Solid growth portion associated with vague trabecular arrangement. Block-like or petaloid eosinophilic deposition was observed in the interstitium (hematoxylin and eosin; bar, 50 μm). e The papillary structure was adjacent to or mixed in with the solid portion. Eosinophilic depositions were also found in papillary cores (hematoxylin and eosin; bar, 50 μm). f Metastatic lesions of the regional lymph nodes. A higher magnification image of the metastatic tumor cells is shown in the inset (hematoxylin and eosin; bars, 500 μm and 20 μm for low- and high-magnification images, respectively). g PAS staining. h Periodic acid-methenamine-silver staining. The deposits were positive for basement membrane materials following periodic acid-Schiff and periodic acid-methenamine-silver staining. Bars, 50 μm