Somatostatinoma

Somatostatinoma

Article
Digestive Health
Diseases & Conditions
+2
Contributed byKrish Tangella MD, MBAAug 21, 2023

What are the other Names for this Condition? (Also known as/Synonyms)

  • D-Cell Tumor of Pancreas
  • Pancreatic D-Cell Tumor
  • Pancreatic Delta Cell Tumor

What is Somatostatinoma? (Definition/Background Information)

  • Somatostatinoma is a very rare, malignant tumor arising from the delta cells (D-cells) of the pancreas. The tumor can arise from the endocrine portion of the pancreas
  • The D-cells of pancreas produce the somatostatin hormone, which is a key hormone that controls and regulates the secretion of many hormones
  • Somatostatinoma generally occurs in middle-aged and slightly older individuals. These tumors are usually functionally active. These tumors may be small and during the early stages may not cause any significant signs and symptoms
  • Somatostatinomas can cause mild diabetes, fatty stools, diarrhea, and lead to weight loss in the affected individuals. Rarely, they can be present in the liver, lung, or kidney
  • In majority of cases, a complete surgical excision is the preferred mode of treating this malignant tumor. In cases of metastasis (which takes place frequently), a combination of chemotherapy, radiation therapy, and surgical procedures may be used
  • The prognosis of Somatostatinoma depends upon many factors including the stage of the tumor, the age and overall health of the individual 

The pancreas is an important organ of the digestive system.

  • Based on function of the pancreas, it can be functionally divided into 2 parts, namely:
    • Exocrine pancreas, which produces digestive enzymes, and
    • Endocrine pancreas that produces hormones such as insulin, glucagon, and somatostatin. Insulin and glucagon helps with controlling sugar levels in blood
  • 95% of the pancreas is exocrine portion and 5% is endocrine portion. Pancreatic tumors (both benign and malignant) can arise from both the exocrine and the endocrine part
  • Based upon anatomy of the pancreas, it can be divided into 3 main parts, namely the:
    • Head,
    • Body, and
    • Tail
  • Pancreatic tumors can affect the head, body, and tail region of the pancreas. Some tumors can affect one area of the pancreas more than the other areas.

Hence, localizing the tumor site can guide the healthcare provider to arrive at a probable diagnosis.

Who gets Somatostatinoma? (Age and Sex Distribution)

  • Somatostatinoma is an extremely rare tumor of the pancreas that occurs in adults in the age range of 40-60 years
  • The incidence of the tumor is 1 in 40 million among the general population
  • It can affect both males and females
  • The condition can occur worldwide; individuals of all racial and ethnic background may be affected

What are the Risk Factors for Somatostatinoma? (Predisposing Factors)

The specific risk factors for Somatostatinoma are generally unknown or unidentified.

  • Familial Somatostatinomas are associated with multiple endocrine neoplasia type 1 (MEN 1, an inherited genetic disorder)
  • A family history of Somatostatinoma or other pancreatic tumors/cancers
  • In some cases, the tumors may arise in the duodenum; in such cases, it may be associated with neurofibromatosis (genetic condition that can cause tumor formation) and pheochromocytoma (a rare neuroendocrine tumor)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Somatostatinoma? (Etiology)

  • The exact cause of Somatostatinoma development is unknown
  • A majority of the tumors occur sporadically (about 95% of them), while the rest are inherited (familial Somatostatinoma)
  • Research scientists believe that the cause of the condition is mostly due to molecular or genetic mutations, which results in tumor formation

What are the Signs and Symptoms of Somatostatinoma?

The signs and symptoms of Somatostatinoma depend upon the size and location of the tumor. During the initial stages, small tumors may not cause any signs and symptoms that are readily recognized. Hence, these tumors are only detected incidentally, when being worked-up for other conditions (i.e., diagnostic tests and exams undertaken for other health conditions).

The signs and symptoms may include the following:

  • Mild diabetes (due to the tumor)
  • Steatorrhea (fatty stools)
  • Nausea and vomiting
  • Abdominal pain, back pain
  • Loss of appetite, weight loss
  • Diarrhea, indigestion
  • Yellowing of skin (jaundice)
  • Dark-colored urine
  • Fatigue (getting tired easily)
  • The presence of gallstones

General features of Somatostatinoma include:

  • This malignant tumor is present in the head of the pancreas. They can arise from the endocrine portion of the pancreas
  • The tumors are generally single and functionally active
  • The average tumor size is 5 cm (they are usually small in size)

How is Somatostatinoma Diagnosed?

Frequently, pancreatic tumors are difficult to detect/diagnose in the early stages. The signs and symptoms can be very similar to other conditions. Since the pancreas is located in the peritoneum, behind many organs, there is a lot of space for the tumor to grow (often unnoticed).

The following are the diagnostic methods that may be used to detect Somatostatinoma:

  • A thorough physical examination and a complete medical history is very important
  • Blood test to check for serum amylase levels
  • Complete blood count with differential
  • Fasting serum somatostatin levels
  • Somatostatin level testing using selective transhepatic portal venous sampling. In this test, the somatostatin levels from various parts of the portal system is measured to localize the tumor
  • Blood tests that may involve tumors markers, such as:
    • Carcinoembryonic antigen (CEA)
    • CA 19.9
    • CA 15.3
    • Alpha fetoprotein
  • Radiological studies that may include:
    • Abdominal ultrasound: A procedure where high-frequency sound waves are used to produce real-time images
    • Endoscopic ultrasound: It is a minimally-invasive procedure that uses high-frequency sound waves to obtain detailed images of the pancreas
    • CT scan of abdomen: It may be helpful in detecting recurrences, or if metastasis to other organs has occurred
    • MRI scan of abdomen: It helps produce high-quality pictures of certain body parts including the tissues, muscles, nerves, and bones
  • Additionally, the following magnetic resonance imaging procedures may be used particularly in individuals suspected of having pancreatic tumor/cancer:
    • MR cholangio-pancreatography (MRCP)
    • MR angiography (MRA)
  • Positron emission tomography (PET) scan: It is particularly helpful in visualizing the spread of the cancer to other body parts (metastasis) and/or recurrence
  • Percutaneous transhepatic cholangiography (PTC): A contrast material is injected into the bile ducts to visualize the structure
  • Endoscopic retrograde cholangio-pancreatography (ERCP): This technique is used when symptoms of pancreatic cancer are present in the individual. A special equipment and dye injections are used to obtain a series of images. If required, a biopsy sample may also be collected during the procedure
  • Invasive diagnostic procedures such as:
    • Laparoscopy: A special device is inserted through a small hole into the abdomen, to visually examine it. If necessary, a tissue sample is obtained for further analysis. Exploration of the abdomen using a laparoscope is called ‘exploratory laparoscopy’
    • Laparotomy: The abdomen is opened through an incision for examination, and if required, a biopsy sample obtained. Exploration of the abdomen using laparotomy procedure is called ‘exploratory laparotomy’
  • Tissue biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination to the pathologist, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

The tissue for diagnosis can be procured in multiple different ways, and they include:

  • Fine needle aspiration (FNA) biopsy of the pancreatic tumor:
    • A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
  • Core biopsy of the pancreatic tumor
  • Open biopsy of the pancreatic tumor

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Somatostatinoma?

The complications due to Somatostatinoma may include the following:

  • When a biopsy of the tumor is performed, it can cause a thromboembolism of the tumor
  • Gastrointestinal obstruction
  • Biliary tract obstruction causing jaundice
  • Compress adjoining organs if the tumor size is large, which may cause the organs to dysfunction or function abnormally
  • Injury to local region
  • If the tumor destroys enough islet cells of the pancreas, it can result in diabetes
  • The tumor can metastasize to the liver and lymph nodes. A majority of individuals have metastasis at the time of diagnosis
  • The presence of tumors in other organs (in rare cases), such as the liver, lung, or kidney

How is Somatostatinoma Treated?

The treatment measures available for Somatostatinoma include the following:

  • In most cases, a surgical excision and removal of the entire tumor is the preferred treatment option. This may be followed by radiation therapy and/or chemotherapy
  • If the tumor has metastasized, then a combination of chemotherapy, radiation therapy, and invasive procedures may be used to treat the tumor. This is often based upon the individual’s specific circumstance
  • Other treatment options may include:
    • Chemotherapy-radiotherapy: Where a combination therapy is used to treat the cancer
    • Targeted therapy: It used to target abnormal cancer cells and reduce the chance of cancer spreading to other parts of the body
    • Biological therapy: Also, known as immunotherapy, where certain bacteria or vaccines are used to indirectly treat the cancer
  • Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals
  • Follow-up care with regular screening and check-ups are important and encouraged

How can Somatostatinoma be Prevented?

Currently, there are no specific methods or guidelines to prevent Somatostatinoma. However, the condition may be avoided through the following measures:

  • Genetic testing in individuals with a family history of pancreatic tumors or other underlying genetic conditions associated with pancreatic tumors
  • Regular medical screening at periodic intervals with blood tests, scans, and physical examinations for those who have already endured the tumor

What is the Prognosis of Somatostatinoma? (Outcomes/Resolutions)

  • Somatostatinoma is a malignant tumor and its prognosis depends upon a set of several factors, which include:
    • Stage of tumor: With lower-stage tumors, when the tumor is confined to site of origin, the prognosis is usually excellent with appropriate therapy. In higher-stage tumors, such as tumors with metastasis, the prognosis is poor
    • The surgical respectability of the tumor (meaning, if the tumor can be removed completely) 
    • Overall health of the individual: Individuals with overall excellent health have better prognosis compared to those with poor health
    • Age of the individual: Older individuals generally have poorer prognosis than younger individuals
    • Whether the tumor is occurring for the first time, or is a recurrent tumor. Recurring tumors have a poorer prognosis compared to tumors that do not recur
    • Response to treatment: Tumors that respond to treatment have better prognosis compared to tumors that do not respond so well to treatment
    • The presence of tumors at other locations
  • An early diagnosis and prompt treatment of the tumor generally yields better outcomes than a late diagnosis and delayed treatment
  • In general, the prognosis of Somatostatinoma is unpredictable. But individuals who respond to therapy have an excellent prognosis
  • Regular follow up visits with the healthcare provider are important

Additional and Relevant Useful Information for Somatostatinoma:

It is estimated that the average lifetime risk of developing pancreatic cancer is about 1.5%.

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Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team

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