Inflammatory pseudotumors of the pancreas and liver with infiltration of IgG4-positive plasma cells.

Recently, it has been reported that autoimmune pancreatitis (AIP) can be complicated with various extrapancreatic lesions. Here, we report a very rare case of pancreatic and hepatic inflammatory pseudotumor (IPT) with the infiltration of IgG4-positive plasmacytes. The patient showed pancreatic and hepatic masses with elevated levels of serum IgG4. Endoscopic retrograde cholangiopancreatography revealed narrowing of the intrapancreatic bile duct. Fluorine-18fluorodeoxyglucose positron emission tomography suggested pancreatic cancer with hepatic metastasis. Histopathologic findings showed fibrosis and infiltration of IgG4-positive plasmacytes, suggesting IPT. The present case suggests a possible common mechanism in the development of AIP and IPT of the liver.