Spectrum of malignant somatostatin-producing neuroendocrine tumors.

OBJECTIVE: To evaluate the clinical manifestations and outcome of patients with somatostatinomas--rare neuroendocrine tumors of pancreaticoduodenal origin.
METHODS: We searched the medical archives and tumor registry of our institution for somatostatinomas or somatostatin-staining tumors for the 12-year period from January 1990 to February 2002. In addition, we reviewed laboratory databases for patients who had an elevated serum somatostatin level. Patients with a neuroendocrine tumor and an elevated serum somatostatin level or somatostatin-positive tumor immunostaining were included in this study.
RESULTS: Eleven patients qualified (9 men and 2 women; median age at diagnosis, 45 years; age range, 22 to 73). The diagnosis of a somatostatinoma was made by immunostaining of the tumor in 9 patients and by finding elevated serum somatostatin levels in 2. Five primary tumors were of duodenal and 6 of pancreatic origin. Psammoma body formation and association with neurofibromatosis were seen only in the duodenal tumors. The known primary tumor sizes varied from 2 to 6 cm. Liver metastatic lesions were present in 6 patients, abdominal lymph node involvement was found in 10 patients, and lung, spleen, and ovarian metastatic involvement was noted in 1 patient each. Diabetes was present in 4 patients (36%) and cholelithiasis in 7 (64%). The presence of a mass led to the diagnosis in most patients with primary duodenal tumors, whereas patients with pancreatic tumors were more likely to have endocrine manifestations. A Whipple procedure was performed in 6 patients, distal pancreatectomy in 3, hepatic artery embolization or ligation in 3, and partial hepatectomy in 1. Cancer-related death occurred in 4 patients, 1 to 8 years after diagnosis (median, 4.5 years). At last follow-up, 2 patients were alive without evidence of disease (8 and 10 years after diagnosis), and 3 were alive with liver metastatic lesions. The status of 2 patients was unclear.
CONCLUSION: Somatostatinomas occurred with approximately equal frequency in the duodenum and the pancreas. The duodenal tumors were more likely to be pure somatostatinomas and have psammoma bodies. Pancreatic tumors were more likely to be multihormonal. Cholelithiasis and diabetes were seen in 64% and 36%, respectively, of the patients. Mass effect of the tumor was the usual manifestation leading to diagnosis. These tumors are slow growing, and long-term survival is possible.