When you are referred to a UCLH specialist by your GP, the doctor will ask you about your general health and any previous medical problems.

They will examine you and take blood samples to check your general health. The following tests may also be carried out:

The doctor passes a thin, flexible tube called an endoscope into your mouth, down your gullet and into your stomach and small bowel. The endoscope has a light and camera at the end, which allows the doctor to see any abnormalities. You may also have samples of tissue (biopsies) taken. These are sent to a laboratory to be tested.

An endoscopy can be uncomfortable, but is not usually painful. Some people have a sore throat after an endoscopy. This gets better after a couple of days.

An endoscopic ultrasound may be used to show the size and position of a gastrointestinal stroma tumour (GIST). It produces an image of the stomach and surrounding structures. It’s done using an endoscope with an ultrasound probe at the end.

You may have samples of tissue (biopsies) taken from the tumour. They will be examined under a microscope.

A special test is done on the biopsy to look for a protein called KIT (CD117). Most GIST cells have this protein.

If you have a tumour that can be removed by surgery, you may not have a biopsy taken before your operation. Instead, the tumour will be sent to the laboratory after the operation for tests to confirm that it is a GIST.

A CT scan takes a series of X-rays that build up a three-dimensional picture of the inside of the body. The scan is painless and takes 10 to 30 minutes. CT scans use small amounts of radiation, which are very unlikely to hurt you or anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

You may be given a drink or injection of a dye that allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. If you’re allergic to iodine or have asthma, you could have a more serious reaction to the injection, so it's important to let your doctor know beforehand.

This test is similar to a CT scan but uses magnetism instead of X-rays to build up a detailed picture of areas of your body. Before the scan, you may be asked to complete and sign a checklist. This is to make sure it’s safe for you to have an MRI scan.

Before having the scan, you’ll be asked to remove any metal belongings, including jewellery. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium and can help the images from the scan show up more clearly.

During the test, you'll be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It's painless but can be slightly uncomfortable, and some people feel a bit claustrophobic during the scan. It’s also noisy, but you’ll be given earplugs or headphones. You'll be able to hear and speak to the person operating the scanner.

A PET scan uses low-dose radioactive sugar to measure the activity of cells in different parts of the body. A very small amount of a mildly radioactive substance is injected into a vein, usually in your arm. A scan is taken a few hours later. Areas of cancer are usually more active than surrounding tissue and show up on the scan.

The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the particular type and the stage of the cancer helps the doctors decide on the most appropriate treatment. Generally, sarcomas are divided into four stages, from 'small and localised' (stage 1) to 'spread into surrounding structures' (stages 2 or 3) or 'spread to other parts of the body' (stage 4). If the cancer has spread to distant parts of the body, this is known as secondary or metastatic cancer.

The stage of the cancer is an important factor in helping your doctors plan the best treatment for you. They also consider other factors. These include: where the cancer started, how fast the cells are dividing and if there are genetic changes (mutations) in the cells. Your doctors will be able to tell you more about this.

If a cancer comes back after initial treatment, it is known as recurrent cancer. It may come back in the tissues where it first started (local recurrence) or it may come back in another part of the body (metastasis).