Fig. 2

Pathological images with hematoxylin and eosin staining and immunohistochemical staining. a A fibrous tumor with inflammatory cells and two foci of calcification. (hematoxylin and eosin (HE), loupe). b High magnification view of the tumor shows storiform pattern by fibroblast-like cells. (HE, × 200 magnification). c Inflammatory cell aggregates were composed of small lymphocytes and plasma cells (HE, × 200 magnification). d IgG-positive plasma cells were located in the inflammatory cell aggregates. (× 400 magnification). e Forty percent of IgG-positive plasma cells expressed IgG4. (× 400 magnification). f Tregs, which express FoxP3, were scattered throughout the mass. (× 200 magnification)