Photomicrographs of histopathological examination. A: Necrotic foci appeared as an area filled with eosinophilic amorphous material (pentagram) [hematoxylin–eosin (HE)-stained, original magnification × 4]. B: Epithelioid spindle-shaped cells form in a storiform and sheet-like growth pattern (HE-stained, original magnification × 20). C: Fine structure of the tumor cells, and especially a typical mitotic figure (yellow arrow) are clearly demonstrated (HE-stained, original magnification × 40). D1: Immunohistochemical staining of EMA was positive (original magnification × 20). D2: Immunohistochemical staining of vimentin was positive (original magnification × 20). E: The Ki67 was estimated at 15%. F: Infiltration of the tumor (arrow) into longitudinal intestinal muscle layer (arrowhead; HE-stained, original magnification × 4).