Duodenal somatostatinomas tend to be smaller and present earlier. The vast majority occur near the ampulla of Vater where they tend to cause obstructive biliary disease (NFI) (39%). Some are associated with neurofibromatosis type 1 and some are occasionally as sociated with phaeochromocytoma. Radiologically they can be difficult to diagnose. This may need endoscopic techniques. At presentation paraduodenal lymph nodes are involved because there is a high malignancy rate, although this is usually low grade. None of the duodenal somatostatinoma patients have developed the full- blown somatostatinoma syndrome but diabetes and gall stones have been noted in some cases.
Recently gain of function hypoxia- inducible factor 2 (HIF 2A) post- zygotic somatic mutations (mosaicism) were detected in ampullary somatostatinoma associated with multiple paraganglioma and polycythaemia. Although originally described only in females it has also been described in males.
Histologically these are psammomatous tumours. Treatment is with surgery if this is feasible, chemotherapy, and, if necessary, hepatic embolization. Somatostatin analogues may lower somatostatin levels and improve symptoms (such as diarrhoea) of both types of somatostatinoma if metastases are present.
Localization
The radiopharmaceutical 68Ga- DOTATATE combined with CT or MRI is superior to previous imaging methods and is now the gold standard in localization of NETs.
treatment
Surgical treatment provides the best chance of cure. If this is not possible, surgical debulking will provide significant relief and prolongs survival rate. Liver resection can be considered with solitary metastasis.
Somatostatic analogues relieve symptoms and inhibit growth. Lanreotide may prolong progression free survival.
Radiotherapy with 177 lutetium (177- lu- octreotate) causes tumour response in those with a high uptake on the OctreoScan; capecitabine can also be used in combination. In ENETS grade 1 and 2 tumours, everolimus or sunitinib may be useful for progressive disease.
treatment outcomes
There is a high prevalence of metastatic disease in somatostatinomas, likely a consequence of late diagnosis. Patients with somatostatinoma tend to have a long survival rate and complete removal of sporadic or hereditary somatostatinoma is usually effective and ensures pro longed survival. Most duodenal somatostatinomas survive and for pancreatic somatostatinoma 10- year survival is around 70%.
