Fig. 2

Histologic findings of SC cases. A Case 1; B–D Case 2; E and F, Case 3 (H&E*). A A tumor consisting mainly of a papillary-cystic growth pattern containing follicular structures. B Low-power view of the biphasic histology of the tumor comprising a HG carcinoma with a solid proliferative component (right portion), and a conventional LG SC with a papillary-cystic component (left portion). The LG component consisted of small, regular cells with an eosinophilic or vesicular cytoplasm (C), whereas the HG component consisted of enlarged, irregularly sized cells with prominent nucleoli, and several mitoses (arrows) can also be observed (D). E Histologic findings of the initial tumor exhibiting the characteristics of LG SC, consisting of tumor cells with unifying nuclear features accompanied with many microcystic structures containing eosinophilic secretions. F Histologic findings in the specimen from the 6th recurrence exhibiting the characteristics of a HG carcinoma, consisting of irregular, enlarged cells containing large pleomorphic nuclei and prominent nucleoli with high mitotic activity (arrows). Scale bars, 100 µm (A, E, F); 500 µm (B); 50 µm (C, D). *Hematoxylin and eosin