[SIGNIFICANCE OF IgG4 IN IDIOPATHIC RETROPERITONEAL FIBROSIS].

(Objective)Retroperitoneal fibrosis is largely divided into the idiopathic and secondary types. Some idiopathic cases include IgG4-related diseases, which are often similar to malignant diseases, such as lymphoma and sarcoma. The diagnostic criteria for IgG4-related disease are used and pathologic examination is necessary for a definitive diagnosis of IgG4-related retroperitoneal fibrosis.