Xanthogranulomatous pancreatitis mimicking a malignant cystic tumor of the pancreas: report of a case.

Xanthogranulomatous pancreatitis (XGP) is a rare inflammatory disease of the pancreas. A correct diagnosis is usually made only after pathological examination. A 76-year-old man was referred to our hospital for investigation of erythroderma, muscle weakness, and weight loss. We suspected dermatomyositis as a paraneoplastic phenomenon and investigated accordingly. Computed tomography showed a cystic lesion encapsulated by a thick wall in the pancreatic body. On magnetic resonance imaging, the lesion had low intensity on the T1-weighted images and heterogeneously high intensity on the T2-weighted images. (18)F-Fluorodeoxyglucose positron emission tomography showed abnormal uptake with a maximum standardized uptake value of 9.1. Based on these findings, we made a preoperative diagnosis of intraductal papillary-mucinous carcinoma and performed a distal pancreatectomy. Macroscopically, the cyst was surrounded by a yellow-tan mass with an unclear border, and was filled with hemorrhagic and necrotic tissue. Microscopically, the mass contained an aggregation of many foamy histiocytes, lymphocytes, and plasma cells. These microscopic findings were consistent with xanthogranulomatous inflammation, and the lesion was diagnosed as XGP. Although it is a rare benign pancreatic lesion, XGP should nevertheless be considered in the differential diagnosis of cystic lesions of the pancreas.