Eosinophilic pancreatitis presenting as rupture of a pancreatic cystic lesion into the chest cavity

A 71-year-old man was receiving follow-up examination because of a retention cyst in the pancreatic body that extended to the dorsal extrahepatic area, but presented to the Emergency Department at our hospital with dyspnea and cough. Chest X-ray showed a large amount of left-sided pleural effusion and abdominal computed tomography (CT) showed reduction in size of the cystic lesion. Biochemical testing of the pleural effusion revealed high levels of pancreatic enzymes. We, therefore, diagnosed rupture of the pancreatic cystic lesion into the chest cavity. Endoscopic retrograde cholangiopancreatography (ERCP) demonstrated stenosis of the pancreatic duct and leakage of contrast medium at the cystic lesion. CT after ERCP revealed leakage of contrast medium from the cystic lesion through the dorsal extrahepatic area into the chest cavity. Endoscopic naso-pancreatic drainage was performed, but the cystic lesion and pleural effusion remained unimproved. Distal pancreatectomy was, therefore, performed. Microscopic examination revealed eosinophilic infiltration of the pancreatic parenchyma, leading to a diagnosis of eosinophilic pancreatitis (EP). Pancreatic retention cyst secondary to chronic pancreatitis associated with eosinophilic infiltration was considered to have ruptured into the chest cavity. EP is a rare etiology of pancreatitis and few cases have been reported. This case was thus considered valuable.