Fig. 2From: A case of idiopathic retroperitoneal fibrosis presenting as gallbladder carcinomaHistology of the retroperitoneal fibrous tissue. Pathology demonstrated dense fibrous tissue with lymphoid plasma cell infiltration (a). Immunohistochemical staining for IgG4 showed that the infiltrated plasma cells were IgG4 negative (> 200/high-power fields) (b, c)Back to article page