Somatostatinomas are a rare type of malignant tumor that grows in or around the pancreas. Doctors may also call them neuroendocrine tumors or islet cell tumors. These tumors secrete large amounts of the hormone somatostatin.
The most common symptoms of somatostatinomas are abdominal pain and unexplained weight loss, but these rarely appear in the early stages. Although somatostatinomas are cancerous, with early diagnosis, they are curable with surgery.
Somatostatinomas occur in only 1 in 40 million people. More than half occur in the head of the pancreas, while the rest tend to grow in the duodenum — the first part of the small intestine.
Approximately 75% of somatostatinomas are cancerous, or malignant.
In this article, we review in more detail the symptoms, causes, and treatment of somatostatinomas and the outlook for people with this tumor.
Somatostatinomas are slow growing tumors. The symptoms are nonspecific, which means that they resemble those of other common medical problems.
Most people do not have severe symptoms until the disease is very advanced. The symptoms are then similar to those that appear in other forms of pancreatic cancer, such as:
- loss of appetite
- nausea and vomiting
- abdominal pain
- frequent diarrhea
- unintentional weight loss
Additional signs and symptoms of somatostatinomas depend on the location of the tumor, which might be in the pancreas or the small intestine.
Somatostatinomas in the pancreas will overproduce a peptide hormone called somatostatin.
Somatostatin helps keep all of the gastrointestinal hormones in balance by blocking their secretion when necessary. Two examples of these hormones are insulin and gastrin.
In less than 10% of cases, this excess of somatostatin leads to somatostatinoma syndrome. People with this syndrome have:
- diabetes (high blood sugar)
- steatorrhea (greasy, fatty, and difficult-to-flush stools)
- cholelithiasis (gallstones)
Somatostatinomas in the duodenum do not cause somatostatinoma syndrome. Instead, the growing tumor causes symptoms. Often, the tumor spreads to the liver and nearby lymph nodes, which may result in a blockage in parts of the intestines or gallbladder tubes.
This obstruction could lead to symptoms such as:
- bloody diarrhea
- jaundice of the skin or whites of the eyes
- a painful and swollen belly
Somatostatinomas are the result of excess delta cells. However, the cause of this overgrowth remains unknown. It can occur in anyone, with or without a history of cancer in the family.
Research suggests that about 37% of somatostatinomas are hereditary. They may occur with other rare genetic syndromes, such as neurofibromatosis, multiple endocrine neoplasia type 1, and Von Hippel-Lindau syndrome.
There are several risk factors for somatostatinomas. These include:
- Genetics: A gene mutation or abnormality can pass down from a parent to a child.
- Age: Most somatostatinomas are slow growing and occur in individuals over the age of 50 years.
- Smoking: Any history of smoking can increase a person’s chance of developing a neuroendocrine tumor of the pancreas.
- Alcohol: Heavy drinking may increase the risk of somatostatinoma growth.
- Pancreatitis: Experts have associated chronic inflammation of the pancreas with an increased risk of somatostatinomas.
- Diabetes: Somatostatinomas are more common in people who have type 2 diabetes.
The vague nature of somatostatinoma symptoms makes these tumors difficult to diagnose, often delaying diagnosis for many months to several years. Doctors usually find somatostatinomas during diagnostic workups for unexplained abdominal pain, weight loss, blood loss, or diarrhea.
A somatostatinomas diagnosis may also occur after a pancreatic cancer surgery biopsy.
Diagnostic tests for somatostatinomas include:
How they differ from VIPomas
VIPomas are another rare type of pancreatic cancer. They usually develop in the pancreas but may also be in the duodenum. People with VIPomas have an oversecretion of vasoactive intestinal peptide (VIP).
VIP blocks the release of hydrochloric acid in the gastric juices, which causes problems with digesting food. As a result, people with VIPomas have frequent and large amounts of watery diarrhea daily.
Doctors usually recommend managing VIPomas with somatostatin analogs.
The only way to cure a somatostatinoma is to remove it completely with surgery. The extent of surgery depends on the size of the tumor and its location in the pancreas. The procedure may just involve the removal of a localized tumor.
If the tumor has spread, it may require a more extensive surgical procedure known as a Whipple procedure. This surgery removes the head of the pancreas, duodenum, gallbladder, bile duct, and lymph nodes.
If complete removal of the tumor is not possible, there are some additional treatment options. These include:
- a procedure called ablation, which uses extreme heat or cold to destroy small tumors
- somatostatin analog medications to slow down hormone production and shrink the tumor
- chemotherapy or specific medications to treat cancer that has spread
- a type of treatment called molecular targeted therapy, which uses drugs or other substances to identify the cancer cells and attack only them
Somatistoma symptoms are vague and can resemble those of many different medical conditions. They may come and go over several months or years.
Any individual who experiences unexplained weight loss, jaundice, abdominal pain, poor appetite, diarrhea, or greasy bowel movements should see a doctor.
Somatostatinomas make up less than 2% of all pancreatic cancers. They are the rarest type of gastrointestinal neuroendocrine tumor.
A person’s outlook will depend on their overall health and the extent of the tumor. If the tumor has not yet spread, surgery offers the best chance of a complete recovery.
The 10 year survival rate for pancreatic somatostatinoma is about 72%. Even when a somatostatinoma has spread, the survival rate is higher than that of the other types of neuroendocrine tumors.
People with somatostatinomas also tend to have a better outlook than those with other types of pancreatic cancer.