Fig. 5

Microscopic and immunohistochemical staining findings. A Hematoxylin and eosin staining of the large cystic tumor. The tumor consisted of spindle-shaped tumor cells showing little atypia and forming interlacing fascicular or bundle arrangements. Nuclear mitosis was scarcely found. No lymphatic, vascular or perineural invasions were observed. The bottom right white bar indicates 200 µm. B Hematoxylin and eosin staining of the round solid tumor. The solid tumor showed basically similar histological features to the cystic tumor, with interlacing fascicular formations or bundle arrangements of spindle-shaped tumor cells. The bottom right white bar indicates 200 µm. C Immunohistochemical staining of the cystic tumor for desmin. The muscle layer of the jejunum showed positive staining for desmin. A laceration of the proper muscle layer and replacement by the tumor without invasion into the lumen side was observed, suggesting that the tumor originated from the proper muscle layer. The bottom right white bar indicates 2 mm. D Immunohistochemical staining for KIT in the cystic tumor. The tumor cells showed positive staining for KIT. The bottom right white bar indicates 200 µm. E Immunohistochemical staining for DOG1 in the cystic tumor. The tumor cells showed positive staining for DOG1. The bottom right white bar indicates 200 µm. F Immunohistochemical staining findings for S100. The tumor cells showed negative staining for S100. The bottom right white bar indicates 200 µm. G Immunohistochemical staining finding for desmin. The tumor cells showed negative staining for desmin. The bottom right white bar indicates 200 µm. H Immunohistochemical staining for KIT. In the proper muscle layer of the adjacent jejunum, between the inner circular muscle layer and the outside longitudinal muscle layer, KIT and DOG1 (data not shown) staining was seen in a thin linear arrangement, which was interpreted to have no association with hyperplasia of c-kit- or DOG1-positive cells, although the investigated portion of the jejunum was limited and short