[A Case of an IgG4-Related Inflammatory Pseudotumor of the Liver Showing Enlargement That Was Difficult to Differentiate from Hepatic Cancer].

A 60-year-old man was admitted for a liver mass(S3), which rapidly increased in size during intraductal papillary mucinous neoplasm(IPMN)follow-up. Although EOB-MRIwas performed, the mass could not be accurately diagnosed as hepatic cancer. Thus, we performed a lateral segmentectomy. In the resected specimen, a solid tumor mass was clearly bound in segment 3 of the liver. Since histopathology revealed no malignant cells and many IgG4-positive cells, we confirmed the diagnosis as IgG4-related inflammatory pseudotumor of the liver. IgG4-related diseases occur in various organs in the body, and they are known to associate with autoimmune pancreatitis and sclerosing cholangitis, but an IgG4-related inflammatory pseudotumor of the liver is a rare disease. It is often difficult to distinguish from hepatic cancer and surgical resection is performed.