Cystic pancreatic neuroendocrine tumors: is preoperative diagnosis possible?

Pancreatic neuroendocrine tumors rarely undergo cystic degeneration leading to a radiologic appearance, which is often interpreted as a pancreatic mucinous cystadenoma or pseudocyst. We reviewed our experience with 38 neuroendocrine tumors, four of which were cystic, and 24 other cystic pancreatic tumors (mucinous cystadenoma [n = 5], cystadenocarcinoma [n = 6], serous cystadenoma [n = 3], solid/cystic papillary neoplasm [n = 3], intraductal papillary mucinous tumor [n = 6], and mucinous adenocarcinoma [n = 1]) managed operatively between 1990 and 2000. This review was undertaken to identify clinical and pathologic features useful for preoperative diagnosis of cystic neuroendocrine tumors. Two of the four patients with cystic neuroendocrine tumors presented with abdominal pain, one patient was asymptomatic, and one patient had hypoglycemia. Three of the four cystic neuroendocrine tumors were identified by CT scan, and none were biopsied preoperatively. Preoperative diagnoses included mucinous cystadenoma in two patients (n = 2), pancreatic cystic neoplasm in one patient, (n = 1) and insulinoma in one patient (n = 1). All four cystic neuroendocrine tumors were benign and were completely resected (distal pancreatectomy [n = 2], enucleation [n = 2]). Cystic neuroendocrine tumors are difficult to diagnose preoperatively because the majority of these tumors are nonfunctional, and CT does not differentiate these tumors from other cystic neoplasms. Cystic neuroendocrine tumors represent a subgroup of pancreatic cystic and neuroendocrine tumors with malignant potential. Their high resectability rate further supports the role of surgical exploration and resection in the treatment of pancreatic cystic neoplasms.