Fig. 5

Pathologic findings. a, b Hematoxylin–Eosin stain showing a high-grade lymphocytic and plasma cell infiltration and fibrosis in all layers without malignant findings. c Immunohistochemical staining of cytokeratin AE1/AE3 showing that the mucosal epithelium of the gallbladder remained normal with no evidence of destruction by lymphocytic infiltration. d Azan stain showing that lymphocytic infiltration was distributed in a laminar fashion in the gallbladder wall. e, f Although there was no obstruction, there was an apparent phlebitis (e: Hematoxylin–Eosin stain, f: EVG stain). g, h More than 10 IgG4-positive cells were observed per high-power field (g: IgG4 immunohistochemical stain), and the IgG4/IgG positive cell ratio exceeded 40% (h: IgG immunohistochemical stain)