Insulinoma | Cancer Research UK
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This page is about insulinoma, a very rare type of neuroendocrine tumour in the pancreas. There is information about


What insulinomas are

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.


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.

Most insulinomas are not cancer and 9 out of every 10 insulinomas (90%) are benign tumours. About 1 in 10 people (10%) have more than one tumour. Around 1 out of 10 insulinomas are cancerous (10%). And in about 1 in 10 people (10%) the cancer has spread to another part of the body when it is diagnosed.

These are usually slow growing tumours. They can develop in any part of the pancreas. They are very rare and only 1 to 3 people in every million develop them each year.

Insulinomas are a type of neuroendocrine tumour. Neuro means nerve and endocrine means hormone producing. Neuroendocrine tumours (NETs) are tumours that develop in cells that are triggered by nerve cells to produce hormones.

Insulinomas belong to a specific group of NETs called gastroenteropancreatic neuroendocrine tumours (GEP NETs). They are also called pancreatic neuroendocrine tumours (pNETs or PETs). 

There is a separate page about neuroendocrine tumours.


Risks and causes of insulinoma

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 of insulinoma

The most common symptoms are caused by changes in insulin levels in the blood. This makes the blood sugar level change suddenly. The symptoms you have are usually when your blood sugar is low. They include

  • Confusion
  • Sweating
  • Weakness
  • Headache
  • Blurred vision
  • Tiredness
  • Forgetfulness, confusion
  • Hunger
  • Feeling sick
  • Sweating
  • Feeling lightheaded
  • Feeling your heart racing (palpitations)

If you don’t eat something when you have very low blood sugar, you may 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 may 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 may include

  • Pain in the tummy (abdomen) or back
  • Diarrhoea
  • Yellowing of your skin and eyes (jaundice)

Tests to diagnose insulinoma

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

If your blood sugar is below 2mmol per litre of blood you will 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 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 insulinomas is surgery. This cures most insulinomas. But surgery is not always possible. Some cancerous insulinomas have already spread when they are diagnosed. If you can’t have surgery you will have drug treatment to control your blood sugar levels and other symptoms.

The treatment you have depends on

  • Whether you have one or more tumours
  • Whether the tumour is benign or malignant
  • Whether the tumour has spread to other parts of the body
  • Where in the pancreas the tumours are
  • Your general health
  • Whether you have a familial cancer syndrome

Other treatments you may have include


The type of surgery you have will depend on

  • Whether you have one or more tumours
  • Where in the pancreas the tumour is
  • The size of the tumour

If the tumour is less than 2cm your surgeon may remove just the tumour. They call this enucleation. If the tumour is in the body or tail of the pancreas you may be able to have the operation with a laparoscope. This is also called keyhole surgery. It is a small operation where the surgeon puts a flexible tube filled with optical fibres (a laparoscope) into the body through a small cut. The surgeon looks through the laparoscope to find and remove the tumour.

If your tumour is in the head of the pancreas, is larger than 2cm, or you have more than one tumour, you may need to have open surgery. This means having an abdominal operation. You will also have an ultrasound scan during your operation, to check for other tumours.

Some people need to have some or all of their pancreas removed. You may also have nearby organs removed. The types of surgery used include

  • Removing the whole pancreas (total pancreatectomy)
  • Removing the head of the pancreas (pylorus preserving pancreaticoduodenectomy – PPPD)
  • Whipples operation – PPPD with part of your stomach removed
  • Removing the tail of your pancreas (distal pancreatectomy)

These are major operations and there are risks with having this type of surgery. But the aim is to try to cure your insulinoma so you may feel it is worth some risks.

You can read more about these operations and the possible side effects on the surgery to try to cure pancreatic cancer page.

If you have MEN 1 or von Hippel-Landau syndrome, you are more likely to develop more tumours after having one removed. Your surgeon may suggest you have more of your pancreas removed than if you didn’t have a family cancer syndrome. This is to reduce the risk of getting more tumours. You are also more likely to need to have an abdominal operation.

Treating symptoms of insulinoma

Some cancerous (malignant) insulinomas are diagnosed when they are already advanced. And some come back after treatment. The most common place for malignant insulinoma to spread to is the liver.

Not everyone with a non cancerous (benign) insulinoma can have surgery. This may be because of other medical conditions or the position of the tumour. If surgery is not possible, you will have treatment to control the amount of insulin the tumours are producing.

The aim of treatment for insulinomas that can’t be completely removed is to control any symptoms you have rather than cure it. Treatments may include


Your specialist may suggest you have surgery even if your malignant insulinoma can’t be completely removed.  Taking away as much of the tumour as possible can help with symptoms because there will be less insulin produced.

If a malignant insulinoma spreads to another part of the body, the most common area it goes to is the liver. You may also have surgery to remove tumours in your liver. As this is a major operation and there are risks, you need to think carefully about the benefits. Will it improve your quality of life enough to make it worth having such a big operation? Your surgeon will talk to you about the risks and benefits and answer any questions you have.

Instead of having a major open surgery for a cancer that has spread to your liver you may be able to have radiofrequency ablation, cryotherapy or transarterial chemoembolisation (TACE) to reduce your symptoms. Or you may have selective internal radiotherapy (SIRT).

Radiofrequency ablation uses heat made by radio waves to kill cancer cells.

Cryotherapy uses a cold probe to destroy cells and tissue by freezing.

TACE is when you have chemotherapy injected directly into the area of the tumour in the liver. You also have an injection of another substance which blocks the blood supply to the tumour. This substance may be a gel or tiny plastic beads and helps to keep the chemotherapy around the tumour.

SIRT is when microscopic beads that are coated with a radioactive substance called Yttrium-90 are injected into the blood supply to the liver. This is a type of targeted radiotherapy.

Before you have surgery you will need to have good control of your insulin levels. You may need to start on one of the drug treatments that control symptoms, for example, diazoxide. If you have MEN1 and have other symptoms because of that, such as a high calcium level, you will also need treatment to control the symptoms.

Drugs and diet to control blood sugar

The symptoms of an insulinoma can be difficult to cope with. To help to control your blood sugar you may need to have a high glucose diet. Being aware of the symptoms of a low blood sugar will help you correct it quickly by eating something that contains glucose.

The drug diazoxide helps to control blood sugar by reducing the amount of insulin you make. You take it as a tablet. The possible side effects include feeling or being sick, loss of appetite, and fluid build up in the legs or other parts of the body.

Other drug treatments that help control blood sugar are verapamil, diphenylhydantoin [pronounced dye-feen-eye-l-hide-an-toe-in] and steroids. Some tumours have somatostatin receptors and then somatostatin analogue drugs such as octreotide and lanreotide can also reduce the amount of insulin in your body. There is information about somatostatin analogues in the carcinoid section of CancerHelp UK.


Chemotherapy can also help to control symptoms of a malignant insulinoma that can’t be removed with surgery. The drugs used may include doxorubicin and streptozocin.


Research into insulinomas

Research is always more difficult with rare conditions. There are fewer people available to take part in a trial, so it takes longer for the trial to recruit enough people.

There is research looking into diagnosing and monitoring these tumours, as well as research into different types of chemotherapy.

New biological treatments include drugs like sunitinib (Sutent), everolimus (Afinitor) and bevacizumab (Avastin). These types of treatment work on tumours that have particular proteins.

A recent phase 3 trial found that people having everolimus for advanced neuroendocrine tumours (NETs) had a longer time before their cancer started growing again compared to people having a dummy drug (placebo). The average time before the tumour started growing again was 11 months, compared to 4.6 months in people having the placebo. 

Another phase 3 trial comparing sunitinib with a placebo for advanced NETs found that the average time before the cancer started growing again was 11.4 months compared to 5.5 months in people having the placebo.

The All Wales Medicines Strategy Group (AWMSG) and the Scottish Medicines Consortium say that sunitinib and everolimus should be available on the NHS. You should be able to have sunitinib or everolimus if other treatments are not working, and you have pancreatic neuroendocrine tumour that cannot be removed with surgery or has spread to other parts of the body. In England NICE have not looked at these drugs for NET. You may be able to have them through individual funding through your PCT or through the cancer drugs fund if your doctor thinks they would be helpful.

We need more research to find out which of these new treatments work best and when to use them. To find out more about trials for neuroendocrine tumours go to our clinical trials database.


Coping with insulinoma

Coping with a rare condition can be difficult both practically and emotionally. Being well informed about your condition and possible treatments can make it easier to make decisions and cope with what happens.

It can also help to talk to people with the same condition. But it can be hard to find someone with a rare tumour. Check out Cancer Chat – Cancer Research UK’s discussion forum. It is a place to share experiences, stories and information with other people who know what you are going through.

You might also find our general coping with cancer section helpful.

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Updated: 20 March 2014