[Serotonin-Producing Pancreatic Neuroendocrine Neoplasm-A Case Report].

We experienced a case of resection of a pancreatic body bearing a serotonin-producing pancreatic neuroendocrine neoplasm( PanNEN). The patient was a female in her 70s. Contrast-enhanced CT of the pancreatic body showed a 12 mm tumor that was well enhanced in the early, portal, and equilibrium phases. The main pancreatic duct was stenosed at the tumor position, and the distal side was dilated. Although the contrast pattern was indicative of PanNEN, the stenosis of the main pancreatic duct suggested the possibility of invasive pancreatic ductal carcinoma. A serotonin-producing subtype of PanNEN, which causes stenosis of the main pancreatic duct despite its small diameter, was included in the differential diagnoses. We performed resection of the pancreatic body and tail with lymph node dissection. Pathological examination indicated that the tumor was PanNEN G1, and immunostaining revealed positivity for serotonin. Most PanNENs are not accompanied by stenosis of the main pancreatic duct. However, it has been reported that even a small-sized serotonin-producing PanNEN is likely to cause main pancreatic duct stenosis owing to its proliferation pattern. Although there are few reports of serotonin-producing PanNENs, an understanding of the characteristic imaging findings of this disease may be useful in the differential diagnosis of pancreatic tumors.