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A CASE OF TUMOR‐FORMING PANCREATITIS WITH A RAPID AND AGGRESSIVE CHANGE

An asymptomatic 51‐year‐old man was found to have a low echoic mass by ultrasonography, 12 mm in diameter, at the head of the pancreas during mass screening. Endoscopic ultrasonography revealed that the mass was hypoechoic with clear margins and without main pancreatic duct dilatation. Therefore, islet cell tumor was suspected, but pancreatic carcinoma could not be excluded. After 3 months, follow‐up ultrasonography revealed that the margin had become more clearly defined and the mass had tended to enlarge. Endoscopic ultrasonography and endoscopic retrograde cholangiopancreatography revealed dilatation of the main pancreatic duct. A pylorus‐preserving pancreaticoduodenectomy was performed for the presumed diagnosis of pancreatic carcinoma. Histological examination revealed prominent fibrosis and destruction of the exocrine parenchyma without evidence of malignancy. The diagnosis of pancreatic carcinoma based on tendency of enlargement and dilatation of the main pancreatic duct was difficult in this case.