Acute pancreatitis secondary to non-functioning pancreatic neuroendocrine tumor: uncommon clinical presentation. Clinical case and review of literature.

Background: Pancreatic neuroendocrine tumors (PNETs) are uncommon, representing <5% of all pancreatic neoplasms, divided into functioning PNETs with secreted hormone cause of specific symptoms, and non-functioning PNETs (nf- PNETs) characterized by delayed diagnosis with metastases and clinical manifestations of compressive effects. Surgical approach is recommended for functioning and nf-PNETs >2 cm in diameter.

Case Report: A 76-year-old woman was admitted to the UOC-University-Surgery Hospital "A. Fiorini" in Terracina for nausea and pain in the upper abdominal quadrants with dorso-lumbar irradiation, arising after the evening meal. After the haematochemistry tests and the instrumental investigations, the diagnosis of acute, severe halitiasic pancreatitis was made. Conventional US, CCT, CE-MRI and EUS showed a 2.8cm diameter lesion in the head-body junction of the pancreas. FNA-cytological examination did not found the presence of atypical pancreatic cells. Total-body scintigraphy with Octreoscan® documented a pathological hypercaptation area located in correspondence with the neoformation. The patient underwent a body-tail spleno-pancreatectomy. The histological examination showed an intermediate grade (G2) nf-PNET infiltrating the lienal vein and stenosing the Wirsung duct, with perilesional pancreatitis. Immunohistochemistry showed CAM 5.2, Synaptophysin (>95%) and Chromogranin (60%) positive immunophenotype, with negative intratumoral Somatostatin expression.

Conclusion: Although rarely, nf-PNETS may be the cause of severe non-biliary acute pancreatitis from pancreatic ductal system compression. In cases where PET/CT68Ga cannot be performed, total-body scintigraphy with Octreoscan® remains the most widely used method for the diagnosis of PNETs and the identification of extra-pancreatic lesions. Chromogranin and Synaptophysin are confirmed as specific markers of neuroendocrine differentiation.

Key Words: Acute pancreatitis, Chromogranin, Pancreatic neuroendocrine tumor, Synaptophysin, Somatostatin.