| [ Summary ] |
Pancreatic swelling or masses observed in type 1 autoimmune pancreatitis (AIP) comprise of thickening and swelling of various microscopic structures, such as the peripancreatic region, pancreatic ducts, lobules, vessels and nerve fibers. Despite the dense inflammatory infiltrate, tissue damage caused by type 1 AIP seems to be minimal, and the target of the inflammation is still unknown. Severe inflammatory infiltrate may represent a kind of lymphoproliferative disorders. In contrast, type 2 AIP is an exocrine‒centered inflammatory reaction with neutrophilic infiltration. A spectrum of histological changes associated in inflammation including degeneration, extinction and regeneration are observed in the epithelium, and ductal epithelium and acinar cells are considered to be the targets of the inflammation. The histological features are nonspecific, resembling Helicobacter pylori‒associated gastritis and inflammatory bowel disease, and thus the etiology is hard to speculate. Type 2 AIP could be a histological reaction caused by a variety of differing etiologies. |