Imitators of chronic pancreatitis: diffuse neuroendocrine tumour of the pancreas

We report a rare case of diffuse replacement of the pancreas with neuroendocrine tumour mimicking chronic pancreatitis. A 55-year-old female with no significant past medical history initially presented with abdominal pain in 2006. A CT of the abdomen and pelvis was performed, revealing diffuse pancreatic parenchymal calcifications with mild pancreatic ductal dilatation and no discrete mass. She was diagnosed with chronic pancreatitis and followed clinically until 2015, where she presented with recurrent abdominal pain. A repeat CT and MRI of the abdomen were performed which revealed new hypoenhancing masses within the pancreas, particularly in the pancreatic tail. There was a persistent background of pancreatic parenchymal calcifications. The possibility of pancreatic neuroendocrine tumour was raised, and an indium-111 Octreotide scan was recommended. Diffuse intense uptake was identified throughout the pancreas on the indium-111 imaging. Given the concern for neuroendocrine tumour, a total pancreatectomy was performed, with histopathology revealing replacement of the pancreas with coalescing well-circumscribed nodules. Many of the nodules had numerous calcifications and localized amyloid deposition. Immunohistochemical stains of the neoplastic cells were strong for neuroendocrine markers chromogranin A and synaptophysin. Overall the findings were consistent with numerous neuroendocrine tumours of the pancreas, Grade II, as per the 2010 WHO criteria for neuroendocrine tumours of the pancreas. Neuroendocrine tumours of the pancreas are lesions that arise from the islet cells, with an approximate incidence of five cases per million people per year. Only one other case report has been documented in the literature by Singh et al demonstrating diffuse pancreatic neuroendocrine tumour replacing the entire pancreas. As diffuse pancreatic neuroendocrine tumour can look similar on imaging to chronic pancreatitis or other infiltrative processes, we wanted to present this case and some of the more specific imaging findings in distinguishing these entities.