Carcinoma ((a) and (b)) and nonneoplastic ((c) and (d)) areas at the mucosal surface of gall bladder cancer. Severe inflammation ((a) and (c)) and many IgG4-positive cells ((b) and (d)) were found in both neoplastic and nonneoplastic areas. (a) and (c) hematoxylin and eosin stain (HE); (b) and (d) IgG4 immunohistochemistry.
