Somatostatinoma syndrome

Abstract

SUMMARY
Somatostatinomas are extremely rare functioning endocrine
tumors of the gastrointestinal tract, occurring with almost
equal frequency in the pancreas (mainly in the head) and
duodenum (periampullary region). The latter are often associated
with von Recklinghausen disease (50%). They occur
sporadically (93.1%) or as part of multiple endocrine
neoplasia type 1 (6.9%). The tumors are relatively large
(with an average size of 5 cm for those of pancreatic and 2.5
cm for those of duodenal origin) and usually malignant
(64.7%) with metastases mainly to the lymph nodes (31.2%)
and liver (27.7%). Duodenal somatostatinomas are characterized
by the frequent presence of psammoma bodies. Clinical
manifestations are characterized by two distinct entities,
one due to somatostatin hypersecretion (inhibitory
syndrome) and the other due to tumor location and growth.
The inhibitory syndrome includes diabetes mellitus or glucose
intolerance, cholelithiasis, weight loss, diarrhea with
or without steatorrhea, and hypochlorhydria or complete
achlorhydria. Clinical manifestations due to tumor location
and growth include mainly obstructive jaundice, duodenal
obstruction, weight loss, and gastrointestinal bleeding.
Mixed clinical manifestations may occur in cases of
multiple hormone secretion by the tumor (e.g. Cushings
syndrome, peptic ulcer etc.). The diagnosis is usually accidental
at the time of laparotomy for cholecystectomy or
during gastrointestinal imaging studies for various nonspecific
complaints. For the definitive diagnosis of somatostatinoma
histology with immunocytochemistry is mandatory. The localization of tumor or metastases may
be made by imaging methods, mainly by endoscopic U/S
(87.2%), and angiography (82.1%) or by surgical exploration.
Treatment of choice is the surgical removal of tumor
and, when possible, of metastases, with or without adjuvant
chemotherapy. Due to their slow natural course, somatostatinomas
have a better prognosis than pancreatic or
biliary duct cancer.