Fig. 1

Histological findings. a A proliferation of benign-appearing eosinophilic spindled cells expanded the lamina propria and separated colonic crypts with serrated architecture (haematoxylin and eosin, original magnification 40×). b The proliferation of spindled cells was separated from the surface epithelium by a zone of uninvolved but inflamed lamina propria (haematoxylin and eosin, original magnification 100×). c Conspicuous hemosiderin deposition occurred at the interface of the spindle cell proliferation and the inflamed lamina propria (haematoxylin and eosin, original magnification 200×). d A Perls’ Prussian blue stain confirmed the presence of hemosiderin (original magnification 400×)