Answer: Autoimmune pancreatitis

Histology: The resected specimen revealed a duct-centric mixed inflammatory infiltrate composed of plasma cells and eosinophiles. In addition, a prominent venulitis is noted.

Discussion: Autoimmune (lymphoplasmacytic sclerosing) pancreatitis is a distinctive form of chronic pancreatitis characterized by a ductcentric mixed inflammatory infiltrate and a prominent venulitis. The inflammatory infiltrate is composed of a mixture of lymphocytes, plasma cells and eosinophiles with some neutrophiles. Autoimmune (lymphoplasmacytic sclerosing) pancreatitis occurs more commonly in men than women with a male to female ratio of 2:1. Of interest, a significant fraction of these patients have a personal history of autoimmune disease such as Sjögrens, sclerosing cholangitis, chronic idiopathic inflammatory bowel disease, retroperitoneal fibrosis, or thyroiditis. Serum IgG4 levels are elevated above 135 mg per deciliter in the majority of cases. Some patients also have autoantibodies to carbonic anhydrase II and/or lactoferin.

Immunohistochemical labeling can be used to demonstrate that the majority of the lymphocytes in the pancreas are T-cells and that there is an increase number of IgG4 expressing plasma cells (>10 per high power field).

The literature now makes it clear that autoimmune (lymphoplasmacytic sclerosing) pancreatitis is one of a number of IgG4 related systemic sclerosing diseases. These include sclerosing cholangitis, idiopathic retroperiphenial fibrosis (Ormand disease), chronic sclerosing sialadenitis (Küttner tumor), plasma cell granuloma of the lung, and sclerosing lymphoplasmacytic tubulointerstitial nephritis.