Fig. 5

Histopathological examination by hematoxylin and eosin staining. a Solid tumor cells have oval nuclei and vacuoles in basophilic, polygonal, or cubic cytoplasm. Tumor cells exhibit papillary proliferation. Slightly basophilic, uniform structures are present in the interstitial tissue and cytoplasm. b Some of the tumor cells have a follicular pattern. One or two layers of tumor cells surround the follicles and proliferate in a follicular shape. The follicles are composed of uniform and basophilic material that resembles mucous material