Somatostatinomas are rare tumours that arise from specialised cells in the pancreas or duodenum (first part of small intestine) that produce large amounts of the hormone somatostatin.

Alternative names for somatostatinoma

Functional pancreatic neuroendocrine tumour

What are somatostatinomas?

Somatostatinomas are part of a group of rare tumours called functional pancreatic neuroendocrine tumours. These tumours arise from specialised D (delta) cells present in the pancreas or duodenum. They produce large amounts of the hormone somatostatin.

Somatostatin is a hormone produced by the hypothalamus, pancreas and gastrointestinal tract, which inhibits the release of other hormones such as insulin, glucagon, growth hormone, gastrin, secretin and cholecystokinin. It reduces gastrointestinal motility and gastric secretions. It also inhibits pancreatic secretions and gall bladder contraction.

Patients with a somatostatinoma are prone to developing insulin resistance and diabetes mellitus, gallstones (due to reduced gall bladder contraction), loose fatty stools (due to reduced secretion of enzymes involved in the digestion of fatty food) and weight loss.

What causes somatostatinomas?

Somatostatinomas are caused by increased production of specialised D cells in the pancreas or duodenum. The malignant tumour cells may spread to adjacent lymph nodes and liver. The exact trigger for their uncontrolled division is not known. Most of these tumours occur for no known cause, although for about 1 in 10 patients they may occur due to a genetic condition such as multiple endocrine neoplasia type 1 or neurofibromatosis type 1.

What are the signs and symptoms of somatostatinomas?

Somatostatinomas can have two distinct types of symptom presentation depending upon the location of the tumour.

  1. Somatostatinomas that arise from the pancreas are associated with symptoms due to excessive production of somatostatin. These include development of diabetes mellitus or worsening of glucose control; abdominal pain/nausea due to gallstones; fatty/loose stools; and reduced acid production in the stomach.
  2. The tumours that arise from the duodenum mostly lead to symptoms due to mechanical obstruction of the small intestine such as abdominal pain/discomfort; nausea; and vomiting.

In the majority of patients, the tumour will have spread to the liver or adjacent lymph nodes (metastasis) at the time of diagnosis; patients may have jaundice and significant weight loss.

How common are somatostatinomas?

Somatostatinomas are extremely rare tumours affecting about 1 person in every 40 million. Most patients are in their 40s-60s. Men and women are affected in equal numbers.

Are somatostatinomas inherited?

Most of the somatostatinomas are sporadic; although they may run in families as part of multiple endocrine neoplasia type 1 syndrome or neurofibromatosis type 1.  

How are somatostatinomas diagnosed?

Most somatostatinomas are diagnosed by radiological imaging studies such as computerised tomography (CT) or endoscopy, which is usually carried out for the investigation of unexplained abdominal pain, weight loss or diarrhoea. Endoscopy involves inserting a long flexible tube with a camera attached to the end, through the patient's throat, for example. It is used to collect images of the inside of your body.

In patients suspected to have somatostatinoma, initial blood tests may show elevated somatostatin hormone levels. A CT scan of the abdomen is used to look for primary tumours in the pancreas or duodenum as well as assessing any spread of the disease locally (lymph nodes) or distant spread to the liver.

Somatostatin receptor scintigraphy (octreoscan) is a specialised investigation available in a limited number of centres, which helps in localisation of the tumour and assessing tumour spread. In case the tumour is localised to the duodenum or pancreas, an endoscopic ultrasound may be carried out.  

The diagnosis of somatostatinoma can only be confirmed if a tissue sample from a suspected patient with this condition is obtained (on biopsy/post surgery), marked with special stains and assessed under the microscope.

How are somatostatinomas treated?

Exact treatment will vary between patients and be tailored to their individual needs. The definitive treatment for a somatostatinoma is surgical removal of the tumour, wherever possible. However, in most patients the tumour will have spread to the liver making surgical removal of the tumour more difficult. If surgery is not possible, reduction of the tumour’s spread may be attempted (whenever possible) that may involve removal of the primary tumour or liver metastasis. In cases where the tumour has spread to the liver (liver metastasis), a segment of liver may be removed surgically or by introducing a chemical /blood clot to the artery supplying blood to the area of the tumour, which will cause that part of the tissue to die. This technique is known as chemo-embolisation.

Medical treatment of somatostatinoma includes use of chemotherapy with chemotherapy drugs such as 5-Flourouracil, Streptozocin or doxorubicin.

Somatostatin analogues such as Octreotide/Lanreotide are not useful in patients with somatostatinoma.  

In patients with diarrhoea and malabsorption, addition of pancreatic enzyme supplements and a balanced diet is helpful.

Are there any side-effects to the treatment?

Surgical treatment is associated with general risks common to all types of surgery such as bleeding and infection.

Chemotherapy is associated with side-effects such as reduced immunity to infections, nausea, vomiting and alopecia (hair loss). Patients should discuss any concerns with their doctor or specialist.

What are the longer-term implications of somatostatinomas?

The long-term prognosis of somatostatinoma depends on whether or not the cancer has spread to the liver. Patients may need to take long-term medication to control associated conditions such as diabetes mellitus. If the tumour is caught early before spread to the liver and can be removed by surgery, patients have a much improved prognosis. Eating a balanced diet and having a healthy lifestyle can also help in the management of somatostatinoma. 

Last reviewed: Jan 2017