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Overview
Tests to diagnose stomach cancer include an endoscopy and biopsy, which can look inside the oesophagus and check for cancer cells, as well as blood tests and imaging tests.
The test results also help show how large the cancer is and whether it has spread. This is called staging.
What's on this page
If your GP suspects that you have stomach cancer, they will examine you, arrange initial tests and refer you to a specialist such as a gastroenterologist.
Tests
Endoscopy and biopsy
The main tests are endoscopy and biopsy. These tests are often done at the same time.
An endoscopy (also called a gastroscopy or upper endoscopy) lets your doctor look inside your stomach and small bowel. It is usually done as day surgery. Before the test, you will probably need to fast (not eat or drink) for about 6 hours.
You will usually have a light sedation to make you sleepy. A general anaesthetic is only needed in a small number of cases. Once the sedative has taken effect, a long, flexible tube with a light and small camera on the end (endoscope) will be passed into your mouth, down your throat and oesophagus, and into your stomach and small bowel.
If the doctor sees anything unusual during the endoscopy, they may take a small sample of tissue. This is called a biopsy. A pathologist will check the sample under a microscope to look for cancer.
The endoscopy takes about 10 minutes. You might feel sleepy after, so someone will need to take you home. You may also have a sore throat or feel bloated for a short time.
Endoscopic ultrasound (EUS)
You may have an EUS at the same time as a standard endoscopy. The doctor will use an endoscope with an ultrasound probe on the tip or with a built-in ultrasound device. The probe releases soundwaves that echo when they bounce off anything solid, such as an organ or tumour.
This test helps work out whether the cancer has spread into the oesophageal or stomach wall, nearby tissues or lymph nodes. During the EUS, your doctor may use the ultrasound to guide a needle into the area they want to look at and take tissue samples.
Further tests
If a biopsy shows you have stomach cancer, you may have more tests to see if the cancer has spread. This is called staging. Some tests may be repeated during or after treatment to check your health and how well treatment is working.
Blood test
What it is: A sample of your blood is checked.
Why it’s done: Checks your general health, checks for low red blood cell count (anaemia), and sees how your liver and kidneys are working.
What to expect: Quick test, usually a small needle in your arm.
Imaging scan
What it is: Pictures of the inside of your body using CT, MRI or PET–CT scans.
Why it’s done: Checks if the cancer has spread to other parts of your body.
What to expect: You’ll lie still on a table. For some scans, a liquid dye (contrast) is injected into a vein.
Laparoscopy
What it is: Keyhole surgery using a thin tube with a camera.
Why it’s done: Checks if cancer has spread to the stomach’s outer layer or the abdomen lining.
What to expect: Done under general anaesthetic. The tube is inserted through small cuts in your belly. Afterwards, you may feel bloated or have shoulder pain.
Genomic testing
What it is: Special tests on tissue removed during surgery.
Why it’s done: Finds gene changes (mutations) in cancer cells. This helps decide which treatments may work best.
What to expect: Uses tissue already taken during surgery or biopsy. No extra procedure is needed.
Sometimes an endoscopic resection is used to help stage stomach cancer, but it can also be a treatment for early-stage stomach cancer.
Staging
Working out how far the cancer has spread is called staging. It helps your doctors recommend the best treatment for you.
The TNM (tumour, node, metastasis) staging system is used to stage stomach cancer. Lower numbers mean the cancer is less advanced.
- T shows how big the tumour is (T1–T4)
- N shows if lymph nodes have cancer (N0–N3)
- M shows if the cancer has spread to other parts of the body.
The TNM scores are combined to work out the overall stage of the cancer, from stage 1 to stage 4. Ask your doctor to explain what the stage of the cancer means for you.
The stages of stomach cancer are:
- Stage 1 (early cancer) – tumours only in the stomach
- Stages 2-3 (locally advanced cancer) – tumour has spread deeper into the stomach wall and to nearby lymph nodes
- Stage 4 (metastatic or advanced cancer) – tumours have spread beyond the stomach wall to nearby parts of the body or lymph nodes, or to more distant lymph nodes and other parts of the body.
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