Fig. 2
The histopathologic finding of the tumor revealed a type AB thymoma (World Health Organization classification) with the ectopic thymic tissue (hematoxylin and eosin staining). a In lymphocyte-poor areas, the oval- to spindle-shaped neoplastic cells were arranged in a fascicular pattern. b In lymphocyte-rich areas, polygonal-shaped neoplastic cells were arranged with vesicular nuclei in dense chromatin. In lymphocyte-rich areas, a diffuse proliferation of polygonal-shaped neoplastic cells was observed with vesicular nuclei and small nucleoli. c, d Foci of the ectopic thymic tissue with Hassall’s corpuscles were found adjacent to the tumor capsule. Original magnification: × 100 (a, b, d), × 40 (c)