Gastrointestinal stromal tumours (GISTs) are rare cancers that develop in the digestive system. They are a type of soft tissue sarcoma. GISTs are most common in people aged 60 to 65 and are rare in people under the age of 40.
Most GISTs start in the stomach or small bowel. But they can develop anywhere along the length of the digestive system (gastrointestinal tract). For example, they may also start in the gullet (oesophagus) or the back passage (rectum). Rarely, they can develop outside the digestive system.
Anatomy of the bowel
Booklets and resources
The symptoms you have depend on the size of the tumour and where it is in the digestive system. Symptoms may include:
- discomfort or pain in the tummy (abdomen)
- being sick (vomiting)
- blood in your poo (stools) or vomit
- anaemia (low level of red blood cells)
- a painless lump in the tummy
- feeling tired and weak (fatigue)
- a high temperature (fever) and sweating at night
- losing weight for no obvious reason.
These symptoms can be caused by conditions other than a GIST, but you should always have them checked by your doctor.
Some people do not have symptoms. They are diagnosed with GIST by chance when having a test or scan for another reason.
The causes of GISTs are unknown, but research is trying to find out more.
Most people who have a GIST do not have a family history of the condition. But there are very rare cases where several family members have been diagnosed with a GIST.
People with a genetic condition called neurofibromatosis (NF) have a slightly increased risk of a GIST.
You usually start by seeing your GP, who will examine you. You may also have blood tests to check your general health and the number of cells in your blood (blood count).
If your GP is not sure what the problem is, or thinks your symptoms could be caused by cancer, they refer you to a specialist doctor.
At the hospital, the specialist doctor will ask you about your symptoms and your general health. They will examine you and arrange some of the following tests.
Tests for GIST
There are different tests that might be used to help diagnose GIST. Our cancer support specialists or your specialist doctor or nurse can give you information about any tests we do not explain here.
This test uses a thin tube called an endoscope which has a light and camera on the end. They gently pass the endoscope down into your throat to look inside the gullet, stomach and part of the small bowel.
Endoscopic ultrasound (EUS)
An endoscopic ultrasound uses an endoscope with an ultrasound probe at the end. The probe uses soundwaves to make a picture of the inside of the stomach and the surrounding area. It can help show the size and position of the tumour.
Your doctor or nurse may take samples of tissue from the tumour. This is called a biopsy. This may be done during an endoscopy. The samples are looked at under a microscope. If you have surgery you may not have a biopsy taken before your operation. Instead, the tumour is sent to the laboratory after the operation to find out if it is a GIST.
We have more information about having a biopsy in our information about diagnosing soft tissue sarcoma.
Testing the cancer cells for genetic changes
The laboratory will also test cells from the biopsy or surgery to look for genetic changes in the tumour cells. These changes are called mutations. They can tell doctors whether treatment with targeted therapy drugs is likely to be helpful.
The stage of a cancer describes its size and whether it has spread from where it started.
The grade of the GIST is how fast the cancer cells are growing and dividing. This is called the mitotic rate.
There are two grades:
- G1 (low grade) – the cancer cells have a low mitotic rate, they are growing slowly and are less likely to spread.
- G2 (high grade) – the cancer cells have a high mitotic rate, they are growing faster and are more likely to spread.
Knowing the grade and stage helps your doctors decide on the best treatment for you
Staging of GIST
The most commonly used systems for staging GISTs are the TNM staging system and a number staging system.
TNM stands for tumour, node and metastasis:
- T describes the size of the tumour.
- N describes whether the cancer has spread to the lymph nodes.
- M describes whether the cancer has spread to another part of the body, such as the liver or lungs. This is known as metastatic or secondary cancer.
Doctors put numbers after the T, N, and M that give more details about the size and spread of the cancer.
Information from the TNM system and the grade of the cancer can be used to give a number stage. The number staging system is different depending on where the GIST has started. GISTs are usually divided into 4 stages:
- Stage 1 – the cancer is small, low-grade and has not spread.
- Stage 2 and 3 – the cancer is bigger and may be either low-grade or high-grade, but has not started to spread.
- Stage 4 – the cancer has started to spread to nearby lymph nodes or other parts of the body.
Your doctor or specialist nurse can give you information about the stage and grade of the GIST.
A team of specialists meets to discuss the best possible treatment plan for you. This is called a multidisciplinary team (MDT). Treatment of a GIST depends on different things, including:
- where the GIST is in the body
- the size of the tumour
- the grade of the GIST (its mitotic rate)
- your general health
- if the GIST cells have certain genetic changes.
Your doctor and nurse will talk to you about the best treatment for you. They can talk to you about things to think about when making treatment decisions.
The main treatments for a GIST are surgery and targeted therapy drugs. Chemotherapy is not a helpful treatment for GISTs. Radiotherapy is rarely used.
After surgery to remove a GIST, doctors decide whether it is low-risk or high-risk. They look at where the GIST started, its size and mitotic rate. A tumour that bursts during surgery is also high-risk.
Because high-risk GISTs are more likely to come back your doctor will usually advise treatment with targeted therapy after surgery.
Some small GISTs grow very slowly and may not need treatment. If the GIST is less than 2cm and is not causing symptoms, your doctor might suggest monitoring the tumour. You will have regular endoscopies or scans. If the tumour starts to grow, you can then have surgery.
Targeted therapy drugs called tyrosine kinase inhibitors (TKIs) are used to treat GIST. In more than 8 out of 10 GISTs (about 85%), the tumour cells have a change in a protein called KIT. This change (called a mutation) means the GIST cells constantly get signals telling them to grow and multiply. TKIs block these signals. Tests on the cancer cells are done first to find out how helpful these drugs are likely to be. Imatinib is a TKI drug given:
- before surgery, to reduce the size of the GIST and make surgery more effective
- after surgery, for 3 years, to reduce the risk of GIST coming back (called adjuvant therapy)
- to treat a GIST that cannot be operated on or has spread to other parts of the body.
If the GIST is bigger than 2cm, you may have surgery to remove it. You may have targeted therapy before surgery to shrink the tumour. If the GIST is found to be high-risk, you usually have targeted therapy after surgery.
The surgeon removes the tumour, along with some surrounding healthy tissue. If the tumour has started to grow into other organs close by, the surgeon may also remove these.
Your surgeon will tell you about any possible effects of the surgery. These depend on the size of the tumour and where it is in the body. If the GIST is in the small bowel, you may have an operation to remove part of the small bowel. This does not usually have any long-lasting side effects. If the GIST is in the stomach, you may have part or most of the stomach removed. A specialist dietitian can give you advice and support.
Surgery may also be used to treat GISTs that come back after treatment. We have more information about surgery for soft tissue sarcoma.
You may be offered some treatments as part of a clinical trial.
If a GIST comes back
If a GIST comes back after treatment it may come back where it first started. This is called a local recurrence. Or it may come back in another part of the body which is called secondary or metastatic cancer.
GIST that comes back is usually treated with targeted therapy. Surgery may also be an option if there is only 1 small new GIST. Your doctor or specialist nurse will talk to you about your treatment options
If GIST comes back in the liver it is called secondary liver cancer. The following treatments may be used:
- radiofrequency ablation (RFA) which uses heat to destroy the cancer cells
- cryotherapy which uses cold to destroy the cancer cells.
These are called tumour ablation treatments.
Some people might have a type of radiotherapy called stereotactic ablative radiotherapy (SABR).
You will have regular check-up appointments at the hospital. Your doctor will examine you and ask about any side effects or symptoms. You will also have blood tests. You may also have an x-ray of your chest or CT scan. If you have any new symptoms between appointments, let your doctor or nurse know.
The effects of your treatment might affect how you think and feel about your body. Talk to your nurse if you have concerns about your body image.
Sex and fertility
Cancer and its treatment can sometimes have an effect on your sex life. If you are worried about this talk to your doctor or nurse. You can read about things that may help in our information on cancer and sex.
Some cancer treatments may affect your fertility. If you are worried about your fertility it is important to talk with your doctor before you start treatment. We have more information about:
- getting pregnant after treatment
- making someone else pregnant after treatment
- LGBTQ+ people and cancer treatment.
Well-being and recovery
Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.
Making small changes such as eating well and keeping active can improve your health and well-being and help your body recover.
Organisations such as Sarcoma UK and GIST Cancer UK can provide information and support. Cancer52 works to improve the quality of life for people with rare cancers. Macmillan is also here to support you. If you would like to talk, you can:
Below is a sample of the sources used in our GIST information. If you would like more information about the sources we use, please contact us at firstname.lastname@example.org
Gronchi A, Miah AB et al. Soft tissue and visceral sarcomas: ESMO-EURACAN-GENTURIS Clinical practice guidelines for diagnosis, treatment and follow-up. Annals of Oncology, 2021; 32, 11, 1348-1365 [accessed May 2022].
Casali PG, Blay JY et al. Gastrointestinal stromal tumours: ESMO-EURACAN-GENTURIS Clinical practice guidelines for diagnosis, treatment and follow-up. Annals of Oncology, 2022; 33,1, 20-33 [accessed May 2022].
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by senior medical editor Fiona Cowie, Consultant Clinical Oncologist.
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