Somatostatinomas


Somatostatinomas

Description, Causes and Risk Factors:

A somatostatinoma, a carcinoid tumor arising from enterochromaffin cells (Kulchitsky cells), is a relatively rare neuroendocrine tumor; the pancreas is the most common site of somatostatinomas. Somatostatin is a cyclic tetradecapeptide widely distributed in normal human tissues and secreted by the hypothalamus, cerebrum, spinal cord, vagus nerve, and D cells in Langerhans islets of the pancreas, stomach, duodenum, and small intestine. Somatostatin inhibits numerous endocrine and exocrine secretory hormones, including insulin, cholecystokinin, pancreatic enzymes, and gastrin. Somatostatin syndrome occurs only with pancreatic somatostatinomas or extrapancreatic tumors larger than 4 cm. Duodenal somatostatinomas are detected relatively earlier and are generally smaller than pancreatic somatostatinomas. They frequently present with abdominal pain, obstructive jaundice, cholelithiasis, vomiting, and abdominal bleeding, rather than typical somatostatin syndrome.

Somatostatinoma is associated with multiple endocrine neoplasia (MEN-1 syndrome) in 7% of cases. Duodenal somatostatinomas are occasionally associated with neurofibromatosis and pheochromocytoma.

Somatostatinomas often simultaneously produce other hormone products, including insulin, gastrin, vasoactive intestinal polypeptide (VIP), glucagon, corticotropin (previously adrenocorticotropic hormone [ACTH]), calcitonin, pancreatic polypeptide, and others. If these products are secreted into the bloodstream in significant quantities, they affect clinical presentation and diagnosis.

Both males and females are equally affected.

Symptoms:

    Gallstones.

  • Weight loss.

  • Diarrhea.

  • Fatty stools.

  • Yellowing of the skin and whites of the eyes called jaundice, which is more common if the tumor develops in the small bowel.

  • Abdominal pain.

  • Blockage in the bowel.

  • Diabetes mellitus, symptoms of diabetes mellitus include feeling thirsty, a dry mouth, passing urine frequently, weight loss, tiredness, and blurred vision.

Diagnosis:

Laboratory Tests: Obtain a fasting serum somatostatin level. The reference range is less than 100 pg/mL, but patients with somatostatinoma syndrome may have elevated levels measurable in nanograms per milliliter (this means increases of 1000-fold or greater). Somatostatinomas are very rare; hence, this test is only available in select centers.

Most somatostatinomas are diagnosed by radiographic imaging studies, such as CT scan, in the work-up of unexplained abdominal pain, or by endoscopy for unexplained blood loss, diarrhea, or in an effort to localize a tumor producing another hormone, such as an insulinoma. It is common for somatostatinomas, particularly those of pancreatic origin, to secrete other hormones in addition to somatostatin). PET scan and somatostatin receptor scintigraphy also may localize these tumors.

Treatment:

Since somatostatinomas have a high malignant potential, aggressive intervention is warranted. Surgical excision offers the only opportunity for long-term cure. Five year survival approaches 100% following complete resection in the absence of metastatic disease, while five year survival in the range of 60% overall is seen in patients with metastatic disease at diagnosis. Resection strategies may include distal subtotal pancreatectomy, pancreaticoduodenectomy (Whipple procedure), or, for smaller duodenal tumors, local excision. These tumors tend to be slow growing, and debulking of extensive disease may offer symptomatic relief and extend survival.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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