Tests for Stomach Cancer

Stomach cancers are usually found when a person goes to the doctor because of signs or symptoms they are having. The doctor will take a medical history and examine the patient. If stomach cancer is suspected, tests will be needed to confirm the diagnosis.

Medical history and physical exam

When taking your medical history, the doctor will ask you questions about your symptoms (eating problems, pain, bloating, etc.) and possible risk factors to see if they might suggest stomach cancer or another cause. The physical exam gives your doctor information about your general health, possible signs of stomach cancer, and other health problems. In particular, the doctor will feel your abdomen for any abnormal changes.

If your doctor thinks you might have stomach cancer or another type of stomach problem, he or she will refer you to a gastroenterologist, a doctor who specializes in diseases of the digestive tract, who will examine you and do further testing.

Upper endoscopy

Upper endoscopy (also called esophagogastroduodenoscopy or EGD) is the main test used to find stomach cancer. It may be used when someone has certain risk factors or when signs and symptoms suggest this disease may be present.

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 lining of your esophagus, stomach, and first part of the small intestine. If abnormal areas are seen, biopsies (tissue samples) can be taken 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 cancer is present.

When seen through an endoscope, stomach cancer can look like an ulcer, a mushroom-shaped or protruding mass, or diffuse, flat, thickened areas of mucosa known as linitis plastica. Unfortunately, the stomach cancers in hereditary diffuse gastric cancer syndrome often cannot be seen during endoscopy.

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

This test is usually done after you are given medication to make you sleepy (sedation). If sedation is used, you will probably need someone to take you home.

Endoscopic ultrasound

Ultrasound uses sound waves to produce images of organs such as the stomach. During a standard ultrasound, a wand-shaped probe called a transducer is placed on the skin. It gives off sound waves and detects the echoes as they bounce off internal organs. The pattern of echoes is processed by a computer to produce a black and white image on a screen.

In endoscopic ultrasound (EUS), a small transducer is placed on the tip of an endoscope. While you are sedated, the endoscope is passed down the throat and into the stomach. This lets the transducer rest directly on the wall of the stomach where the cancer is. Doctors can look at the layers of the stomach wall, as well as the nearby lymph nodes and other structures just outside the stomach. The picture quality is better than a standard ultrasound because of the shorter distance the sound waves have to travel.

EUS is most useful in seeing how far a cancer may have spread into the wall of the stomach, to nearby tissues, and to nearby lymph nodes. It can also be used to help guide a needle into a suspicious area to get a tissue sample (EUS-guided needle biopsy).


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 is really cancer is by doing a biopsy. During a biopsy, the doctor removes a sample of the abnormal area.

Biopsies to check for stomach cancer are most often obtained during 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 are 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 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, adenocarcinoma, carcinoid, gastrointestinal stromal tumor, or lymphoma). 

More testing may be done if a sample contains certain types of cancer cells. For instance, the tumor may be tested to see if it has too much of a growth-promoting protein called HER2. Tumors with increased levels of HER2 are called HER2-positive.

Stomach cancers that are HER2-positive can be treated with drugs that target the HER2 protein, such as trastuzumab (Herceptin®). See Targeted Therapies for Stomach Cancer for more information.

The biopsy sample may be tested in 2 different ways:

  • Immunohistochemistry (IHC): In this test, special antibodies that stick to the HER2 protein are applied to the sample, which causes cells to change color if many copies are present. This color change can be seen under a microscope. The test results are reported as 0, 1+, 2+, or 3+.
  • Fluorescent in situ hybridization (FISH): This test uses fluorescent pieces of DNA that specifically stick to copies of the HER2 gene in cells, which can then be counted under a special microscope.

Often the IHC test is used first.

  • If the results are 0 or 1+, the cancer is HER2-negative. People with HER2-negative tumors are not treated with drugs (like trastuzumab) that target HER2.
  • If the test comes back 3+, the cancer is HER2-positive. Patients with HER2-positive tumors may be treated with drugs like trastuzumab.
  • When the result is 2+, the HER2 status of the tumor is not clear. This often leads to testing the tumor with FISH.

It's also possible that the tumor may be tested to see if it has a certain amount of an immune checkpoint protein called PD-L1. If it does, the tumor may be treated with an immune checkpoint inhibitor such as pembrolizumab (Keytruda®). This type of treatment may be given if other treatments have stopped working. To learn more about this type of immunotherapy, see Immune Checkpoint Inhibitors to Treat Cancer.

See Testing Biopsy and Cytology Specimens for Cancer to learn more about different types of biopsies and tests, how the tissue is used in the lab to diagnose cancer, and what the results will 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 cancerous
  • 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 endoscopy to look for stomach cancer or other stomach problems, as it can miss some abnormal areas and does not 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, the patient drinks a white chalky solution containing a substance called barium. The barium coats the lining of the esophagus, stomach, and small intestine. Several x-ray pictures are then taken. Because x-rays can’t pass through the coating of barium, this will outline any abnormalities of the lining of these organs.

A double-contrast technique may be used to look for early stomach cancer. With this technique, after the barium solution is swallowed, a thin tube is passed into the stomach and air is pumped in. This makes the barium coating very thin, so even small abnormalities will show up.

Computed tomography (CT or CAT) scan

A CT scan uses x-rays to make detailed, cross-sectional images of your body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.

CT scans show the stomach fairly clearly and often can confirm the location of the cancer. CT scans can also show the organs near the stomach, such as the liver, as well as lymph nodes and distant organs where cancer might have spread. The CT scan 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. The patient remains on the CT scanning table while a doctor moves a biopsy needle through the skin toward the mass. CT scans are repeated until the needle is within the mass. A fine-needle biopsy sample (tiny fragment of tissue) or a core-needle biopsy sample (a thin cylinder of tissue) is then removed and looked at under a microscope.

Magnetic resonance imaging (MRI) scan

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

Positron emission tomography (PET) scan

For a PET scan, 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.

Some 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.

PET is sometimes useful if your doctor thinks the cancer might have spread but doesn’t know where. The picture is not detailed like a CT or MRI scan, but it provides helpful information about the whole body. Although PET scans can be useful for finding areas of cancer spread, they aren’t always helpful in certain kinds of stomach cancer because these types don’t take up glucose very much.

Chest x-ray

This test can help find out if the cancer has spread to the lungs. It might also determine if there are any serious lung or heart diseases present. This test is not 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 this procedure is done, it is usually only after stomach cancer has already been found. Although CT or MRI scans can make detailed pictures of the inside of the body, they can miss some tumors, especially very small tumors. Doctors might do a laparoscopy before any other surgery to help confirm the cancer is still only in the stomach and can be removed completely with surgery. It may also be done before chemotherapy and/or radiation if these are planned before surgery.

This procedure is done in an operating room with the patient under general anesthesia (in a deep sleep). A laparoscope (a thin, flexible tube) is inserted through a small surgical opening in the patient’s side. The laparoscope has a small video camera on its end, which sends pictures of the inside of the abdomen to a TV screen. Doctors can look closely at the surfaces of the organs and nearby lymph nodes, or even take small samples of tissue. If it doesn’t look like the cancer has spread, sometimes the doctor will “wash” the abdomen with saline (salt water) this is called peritoneal washing. The fluid is then removed and checked to see if it contains cancer cells. If it does, the cancer has spread, even if the spread couldn’t be seen.

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

Lab tests

When looking for signs of stomach cancer, a doctor may order a blood test called a complete blood count (CBC) to look for anemia (which could be caused by the cancer bleeding into the stomach). A fecal occult blood test may be done to look for blood in stool (feces) that can't be seen by the naked eye.

The doctor might recommend other tests if cancer is found, especially if you are going to have surgery. For instance, blood tests will be done to make sure your liver and kidney functions are normal 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 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 journalists, editors, and translators with extensive experience in medical writing.

National Cancer Institute. Physician Data Query (PDQ). Gastric Cancer Screening. 3/10/2017. Accessed at https://www.cancer.gov/types/stomach/hp/stomach-screening-pdq on November 27, 2017.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Gastric Cancer. v.3.2017. Accessed at www.nccn.org/professionals/physician_gls/pdf/gastric.pdf on November 20, 2017.

Last Revised: December 14, 2017

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