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Tests for Stomach Cancer

Stomach cancer (also known as gastric cancer) is usually found when a person goes to the doctor because of signs or symptoms they are having. If stomach cancer is suspected, exams and tests will be needed to find out for sure. If cancer is found, other tests might then be needed to learn more about it.

Medical history, physical exam, and tests to look for bleeding

When taking your medical history, the doctor will ask about your symptoms (such as eating problems, pain, bloating, etc.) and possible risk factors to see if they might suggest stomach cancer or another cause. The physical exam can give your doctor information about possible signs of stomach cancer or other health problems. In particular, the doctor will feel your belly for anything abnormal.

The doctor might order a blood test to look for anemia (a low red blood cell count), which could be caused by the cancer bleeding into the stomach. A test might also be done to look for blood in your stool (feces) that can't be seen by the naked eye, which could also be a sign of bleeding in the stomach.

If your doctor thinks you might have stomach cancer or another type of stomach problem, they will likely refer you to a gastroenterologist (a doctor who treats diseases of the digestive tract), who will examine you and might do further testing.

Upper endoscopy

Upper endoscopy (also called esophagogastroduodenoscopy or EGD) is the test most often done if the doctor thinks you might have stomach cancer.

During this test, the doctor passes an endoscope, which is a thin, flexible, lighted tube with a small video camera on the end, down your throat. This lets the doctor see the inner lining of your esophagus, stomach, and first part of the small intestine. If abnormal areas are seen, biopsy samples can be removed using instruments passed through the endoscope. The tissue samples are sent to a lab, where they are looked at with a microscope to see if they contain cancer.

Unfortunately, some types of stomach cancers can be hard to see during an endoscopy.

Endoscopy can also be used as part of a special imaging test known as endoscopic ultrasound, which is described below.

In some situations, endoscopy can be used to help remove very early stage cancers. It can also be used to help prevent or relieve symptoms or other complications from stomach cancer, without the need for more extensive surgery. (See Surgery for Stomach Cancer.)

You will most likely be given medicine to make you sleepy (sedation) before the endoscopy.


Your doctor may suspect cancer if an abnormal-looking area is seen on endoscopy or an imaging test, but the only way to tell for sure if it's cancer is by doing a biopsy. During a biopsy, the doctor removes small pieces (samples) of the abnormal area.

Biopsies to check for stomach cancer are most often done during an upper endoscopy. If the doctor sees any abnormal areas in the stomach lining during the endoscopy, instruments can be passed down the endoscope to biopsy them.

Some stomach cancers can start deep within the stomach wall, which can make them hard to biopsy with standard endoscopy. If the doctor suspects cancer might be deeper in the stomach wall, endoscopic ultrasound (described below) can be used to guide a thin, hollow needle into the wall of the stomach to get a biopsy sample.

Biopsies may also be taken from areas of possible cancer spread, such as nearby lymph nodes or suspicious areas in other parts of the body.

Testing biopsy samples

Biopsy samples are sent to a lab to be looked at under a microscope. The samples are checked to see if they contain cancer, and if they do, what kind it is (for example, intestinal or diffuse adenocarcinoma, carcinoid tumor, gastrointestinal stromal tumor [GIST], or lymphoma).

If stomach cancer is found, more lab tests may be done on the biopsy samples to learn more about the cancer cells. This might affect how the cancer is treated. 

HER2 testing: The cancer cells may be tested to see if they have too much of a growth-promoting protein called HER2. Cancers with increased levels of HER2 are called HER2-positive. These cancers can be treated with drugs that target the HER2 protein.

The biopsy sample is usually tested for HER2 using either immunohistochemistry (IHC) or fluorescent in situ hybridization (FISH). Often the IHC test is used first, which gives results on a scale from 0 to 3+.

  • If the results are 0 or 1+, the cancer is HER2-negative, so drugs targeting HER2 aren’t likely to be helpful.
  • If the test comes back 3+, the cancer is HER2-positive, so treatment with drugs targeting HER2 could be an option.
  • When the result is 2+, the HER2 status of the cancer is not clear, so it needs to be tested with FISH to clarify the result.

Testing for other gene or protein changes: The cancer cells may also be tested for other gene or protein changes that might affect treatment. For example:

  • If the cells have a certain amount of an immune checkpoint protein called PD-L1, treatment with an immune checkpoint inhibitor such as pembrolizumab (Keytruda) might be an option.
  • If the cells have high levels of microsatellite instability (MSI-H) or a defect in a mismatch repair gene (dMMR), treatment with an immune checkpoint inhibitor might be an option.
  • If the cells have a high tumor mutational burden (TMB-H), meaning they have many gene mutations, treatment with an immune checkpoint inhibitor might be an option.
  • If the cells have changes in one of the NTRK genes, certain targeted drugs might be an option for treatment.

See Testing Biopsy and Cytology Specimens for Cancer to learn more about different types of biopsies and tests, how they are used to diagnose cancer, and what the results can tell you.

Imaging tests

Imaging tests use x-rays, magnetic fields, sound waves, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including:

  • To help find out if a suspicious area might be cancer
  • To learn how far cancer may have spread
  • To help determine if treatment has been effective

Upper gastrointestinal (GI) series

This is an x-ray test to look at the inner lining of the esophagus, stomach, and first part of the small intestine. This test is used less often than upper endoscopy to look for stomach cancer or other stomach problems, as it can miss some abnormal areas, and it doesn't allow the doctor to take biopsy samples. But it is less invasive than endoscopy, and it might be useful in some situations.

For this test, you drink a white chalky solution containing a substance called barium. The barium coats the inner lining of the esophagus, stomach, and small intestine. (Air might be pumped into the stomach through a thin tube at this time as well.) Several x-ray pictures are then taken. Because x-rays can’t pass through the coating of barium, this outline any abnormal areas in the lining of these organs.

Computed tomography (CT or CAT) scan

A CT scan uses x-rays to make detailed, cross-sectional images of the soft tissues in the body.

CT scans can show the stomach fairly clearly and often can confirm the location of a cancer. CT scans can also show other parts of the body to which stomach cancer might have spread, such as the liver and nearby lymph nodes. This can help determine the extent (stage) of the cancer and if surgery may be a good treatment option.

CT-guided needle biopsy: CT scans can also be used to guide a biopsy needle into a suspected area of cancer spread. For this test, you will lie on the CT scanning table while the doctor moves a biopsy needle through the skin toward the mass. CT scans are repeated until the needle is within the mass. A biopsy sample is then removed and sent to a lab for testing.

Endoscopic ultrasound

Endoscopic ultrasound (EUS) is often used to see how far a cancer might have spread into the wall of the stomach, or into nearby areas or nearby lymph nodes. 

For this test, a small ultrasound probe is placed on the tip of an endoscope. While you are sedated, the endoscope is passed down your throat and into the stomach. The probe is put up against the wall of the stomach where the cancer is. It gives off sound waves and detects the echoes as they bounce back, which are then converted into images. Doctors can use these images to look at the layers of the stomach wall, as well as the nearby lymph nodes and other structures just outside the stomach. 

EUS can also be used to help guide a needle into a suspicious area to get a biopsy sample (known as an EUS-guided needle biopsy).

Positron emission tomography (PET) scan

A PET scan can be useful to help determine the extent of the cancer in the body. For this test, you are injected with a slightly radioactive form of sugar, which collects mainly in cancer cells. A special camera is then used to create a picture of areas of radioactivity in the body. The picture is not detailed like a CT or MRI scan, but a PET scan can look for possible areas of cancer spread in all areas of the body at once.

Many newer machines can do both a PET and CT scan at the same time (PET/CT scan). This lets the doctor see areas that “light up” on the PET scan in more detail.

Although PET scans can be useful for finding areas of cancer spread, they aren’t always helpful in certain kinds of stomach cancer because some types don’t take up much of the radioactive sugar.

Magnetic resonance imaging (MRI)

Like a CT scan, an MRI can show detailed images of soft tissues in the body. But MRIs use radio waves and strong magnets instead of x-rays.

This test is not used as often as CT scans to look for stomach cancer, but it may be helpful in certain situations, such as when looking for tumors in the liver.

Chest x-ray

This test can help show if the cancer has spread to the lungs. It might also be used to help determine if a person has any serious lung or heart diseases, which might affect whether surgery would be a treatment option. A chest x-ray isn’t needed if a CT scan of the chest has been done.

You can read more about imaging tests in Imaging (Radiology) Tests for Cancer.

Other tests


If stomach cancer has already been found, and imaging tests such as CT or PET scans have not shown it has spread to other parts of the body, doctors might do a laparoscopy before any other surgery. This can help confirm the cancer is still only in the stomach, which means surgery to remove it might still be an option.

This procedure is done in an operating room while you are under general anesthesia (in a deep sleep). A laparoscope (a thin, flexible tube with a small video camera on the end) is inserted through a small cut in the belly. This lets the doctor look closely at the surfaces of the organs and nearby lymph nodes inside the abdomen, or even remove small samples of tissue, which can then be tested for cancer. 

If it doesn’t look like the cancer has spread, sometimes the doctor will “wash” the abdomen with saline (saltwater). This is called peritoneal washing. The fluid is then collected and checked for cancer cells.

Sometimes laparoscopy is combined with ultrasound to give a better picture of the cancer.

Tests of organ function

If cancer is found, the doctor might recommend certain lab tests, especially if surgery might be an option. For instance, blood tests will be done to make sure your liver and kidneys are working normally and that your blood clots normally. 

If surgery is planned or you are going to get medicines that can affect the heart, you may also have an electrocardiogram (EKG) and/or an echocardiogram (an ultrasound of the heart) to make sure your heart is functioning well.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Ku GY, Ilson DH. Chapter 72: Cancer of the Stomach. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa: Elsevier; 2020.

Mansfield PF. Clinical features, diagnosis, and staging of gastric cancer. UpToDate. 2020. Accessed at on June 30, 2020.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Gastric Cancer. v.2.2020. Accessed at on June 30, 2020.

Last Revised: January 22, 2021

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