[A case of poorly differentiated pancreatic adenocarcinoma with spontaneous regression wherein retrospective rim enhancement findings were important for diagnosis].

A 66-year-old man with epigastric pain was admitted to our hospital for further evaluation of a pancreatic mass, as indicated on transabdominal ultrasonography performed by his family doctor. Using various imaging modalities, the 22-mm tumor was diagnosed as a cystic tumor with hemorrhagic necrosis. The tumor diameter reduced to 11mm over the course of 1 month. However, the tumor margin was irregular than that at the initial diagnosis, and circumferential rim enhancement was observed in equilibrium phase computed tomography images. Therefore, we diagnosed the patient with pancreatic ductal adenocarcinoma with a necrotic component. Distal pancreatectomy with splenectomy was performed, and the subsequent histological diagnosis was poorly differentiated adenocarcinoma. This case had an interesting course as described by the diagnostic images.