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About insulinoma

Insulinoma is a very rare type of tumour that develops in the pancreas. 

Insulinomas are rare tumours that start in the insulin making cells of the pancreas. These cells are called pancreatic islet cells. Insulinomas are also called islet cell tumours.

What and where the pancreas is

Insulin is a hormone that controls the amount of sugar in the blood. It helps glucose to move from the blood into body cells. Islet cells also make other hormones.

Insulinomas produce insulin. This leads to symptoms of diabetes. Normally, our blood sugar rises when we eat, which signals to the pancreas to produce more insulin. Once the blood sugar has gone back to normal levels the pancreas stops making insulin. When you have an insulinoma the tumour keeps producing insulin. This means your blood sugar level continues to drop. This can lead to dangerously low blood sugar levels.

Some insulinomas also produce other hormones such as gastrin. Gastrin is a protein that makes the stomach produce acid to digest food.

Insulinomas are a type of neuroendocrine tumour (NET). Neuro means nerve and endocrine means hormone producing. Neuroendocrine tumours develop in cells that are triggered by nerve cells to produce hormones. They are a particular type of gastroenteropancreatic neuroendocrine tumour (GEP NET). They are also called pancreatic neuroendocrine tumours (pNETs or PETs).

How common they are

Insulinomas are very rare. Only 1 to 3 people in every million develop them each year.

Risks and causes

We don’t know what causes most insulinomas. Between 5 and 10 out of every 100 people with insulinoma (5 to 10%) have a rare family syndrome, either multiple endocrine neoplasia type 1 (MEN 1) or von Hippel-Landau syndrome.

Symptoms

The most common symptoms are caused by changes in insulin levels in the blood. This makes the blood sugar level change suddenly.

You usually have symptoms when your blood sugar is low. These include:

  • weakness or tiredness
  • headache 
  • blurred vision
  • forgetfulness or confusion
  • hunger
  • feeling sick
  • sweating
  • feeling your heart racing (palpitations) or feeling lightheaded

If you don’t eat something when you have very low blood sugar, you might become unconscious.

Some tumours don’t produce extra insulin and don’t cause symptoms at first. These tumours are called non functioning tumours.

Once they are big enough or have spread to other parts of the body they can cause symptoms. The symptoms are either to do with the tumour pressing on other organs, or producing hormones that affect how other organs work. They can include:

  • pain in the tummy (abdomen) or back
  • diarrhoea
  • yellowing of your skin and eyes (jaundice)

Getting diagnosed

Most insulinomas are not cancer. Around 1 out of 10 insulinomas (10%) are cancerous and around 9 out of every 10 insulinomas (90%) are benign.

Around 1 in 10 people (10%) diagnosed with insulinoma have more than one tumour. And in about 1 in 10 people (10%) the cancer has spread to another part of the body when it is diagnosed.

Insulinomas usually grow slowly. They can develop in any part of the pancreas.

Tests to diagnose

You have a blood sugar test if you have symptoms of low blood sugar. This is quick and easy. The doctor or nurse pricks your finger to get some of your blood. Then they put the blood into a blood sugar testing machine.

If your blood sugar is below 2mmol per litre of blood, you have further blood tests to check the levels of insulin and other hormones in your blood. You may also have blood tests to check for proteins that stop your pancreas making insulin.

Other tests you may have include

  • endoscopic ultrasound
  • CT scan
  • MRI scan

Endoscopic ultrasound is an ultrasound scan done from inside your body. You have an endoscopy, but the endoscope contains a small ultrasound probe. The ultrasound helps the doctor to find areas that might be cancer. They then guide a small needle into the areas to remove a sample of cells (a biopsy).

Treating insulinoma

The main treatment for insulinoma is surgery.

Coping

Coping with a diagnosis of a rare cancer can be especially difficult, both practically and emotionally. Being well informed about your cancer and its treatment can make it easier to make decisions and cope with what happens.

Talking to other people

Talking to other people who have the same thing can also help.

Our discussion forum Cancer Chat is a place for anyone affected by cancer. You can share experiences, stories and information with other people who know what you are going through.

The Rare Cancer Alliance offer support and information to people affected by rare cancers.

Last reviewed: 
20 Mar 2014
  • Principles and Practice of Oncology (8th edition)

    DeVita and others

    Lippincott, Williams & Wilkins, 2008

  • Well-differentiated pancreatic tumor/carcinoma: insulinoma

    WW de Herder and others

    Neuroendocrinology, 2006

    Volume 84, Issue 3

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in.

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