Fig. 5

Microscopic findings. Hematoxylin and eosin stain; the tumor consisted of dense collagenous fibers and a complicated proliferation of spindle-shaped cells, which generally appeared heterozygous and homogenous, yet occasionally exhibited nuclear enlargement and mismatch in the center of the tumor. Immunohistochemical stain; the tumor cells were positive for vimentin but negative for S100 protein, synaptophysin, and DOG-1