Metachronous Development of Peritoneal Carcinomatosis in a Patient with Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a rare and unique type of chronic pancreatitis. The prognosis of AIP, particularly when associated with pancreatic cancer or a related malignancy, is not known. Only a few cases, where metachronous pancreas-related cancer developed during follow-up, have been reported. Most of these patients either underwent surgery or steroid therapy. This paper reports a case of a 66-year-old woman with untreated type I AIP who developed peritoneal carcinomatosis more than 2 years later. Initially, the patient had a markedly elevated serum IgG4 level and a diffuse, infiltrative mass-like lesion in the pancreatic head, in which the biopsy results were consistent with type I AIP. The patient was not treated with steroids because of a cerebellar infarction. Twenty-eight months after the diagnosis of AIP, peritoneal carcinomatosis developed without noticeable changes in the pancreas from the initial findings.