Fig. 5

Histologic findings of the colonic polyp biopsy specimen in Case 2. Histologic findings demonstrated the prominent cystic dilation of the crypts (a) (hematoxylin and eosin stain; magnification × 40). Moreover, a mixed inflammatory infiltrate with prominent eosinophils was found (b) (hematoxylin and eosin stain; magnification × 400). IgG-positive plasma cells numbered 60/HPF (c) (IgG-immunostaining; magnification × 400). In the same field, the high number of IgG4-positive plasma cells was found (50 labeled cells per HPF) (83 % IgG4/IgG plasma cells) (d) (IgG4-immunostaining; magnification × 400). Few IgG- and IgG4-positive plasma cells were found after treatment with CyA (e) (IgG-immunostaining; magnification × 400), (f) (IgG4-immunostaining; magnification × 400)