A case of intraperitoneal immunoglobulin G4-related inflammatory pseudotumor.

The term inflammatory pseudotumor (IPT) has been used to describe inflammatory and fibrosing tumoral processes of an undetermined cause that may involve a variety of organ system. IgG4-related disease is a newly recognized fibroinflammatory condition characterized by IgG4-producing plasma cell expansion in affected organs and, often but not always, elevated serum IgG4 concentrations. IgG4-related IPTs, a subtype of IPT, are characterized by dense infiltration of IgG4-positive plasma cells and stromal fibrosis. The association between inflammatory pseudotumor and IgG4 was first reported with a regard to sclerosing pancreatitis. Despite there are many reports on intraperitoneal IPTs including both cellular and lymphoplasmacytic type, only a few cases have been confirmed to be IgG4-related. We experienced a case of intraperitoneal IgG4-related inflammatory pseudotumor in an 83-year-old woman presenting with epigastric pain and malaise. Surgical specimens revealed an IgG4-related inflammatory pseudotumor.