Imaging features of somatostatinoma: MR, CT, US, and angiography.

OBJECTIVE: The imaging features of somatostatinoma are described in four patients.

MATERIALS AND METHODS: Four patients, ranging in age from 24 to 57 years, with somatostatinoma were examined. Ultrasonography (US) and CT were performed in all four patients; MRI and angiography were performed in three patients.

RESULTS: Three patients had a tumor in the pancreas and one in the papilla major. In two cases there were metastases in the liver, and one had bone and lymph node metastases. Pancreatic tumor and metastases were equally well detected by CT and MRI. One tumor in the tail of the pancreas was initially missed by US. Pancreatic tumor and metastases were echo poor. Angiography showed one vascular and one avascular tumor in the pancreas. Chronic obstructive pancreatitis was seen on CT and MRI in the patient with the tumor in the papilla major. Angiography and US failed to demonstrate this tumor; CT and MRI showed the tumor in retrospect. Primary tumor and metastases are of low signal intensity on T1-weighted imaging and increased signal intensity on T2-weighted imaging.

CONCLUSION: Somatostatin-producing endocrine tumors are mainly located in the pancreas but can also be present in extrapancreatic organs such as the duodenum and papilla of Vater resulting in chronic obstructive pancreatitis. Duodenal somatostatinomas are associated with von Recklinghausen neurofibromatosis. Radiologic and MRI features of somatostatinomas resemble those of other neuroendocrine tumors. Radiological techniques and MRI often fail to demonstrate the tumors in the duodenum. The diagnosis in cases of duodenal localization can be established by endoscopic techniques.