Diagnosis of stomach cancer

Last medical review:

Diagnosis is the process of finding out the cause of a health problem. Diagnosing stomach cancer usually begins with a visit to your family doctor. Your doctor will ask you about any symptoms you have and may do a physical exam. Based on this information, your doctor may refer you to a specialist or order tests to check for stomach cancer or other health problems.

The process of diagnosis may seem long and frustrating. It's normal to worry, but try to remember that other health conditions can cause similar symptoms as stomach cancer. It's important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of stomach cancer.

The following tests are usually used to rule out or diagnose stomach cancer. Many of the same tests used to diagnose cancer are used to find out the stage (how far the cancer has spread). Your doctor may also order other tests to check your general health and to help plan your treatment.

Health history and physical exam

Your health history is a record of your symptoms and risks and all the medical events and problems you have had in the past. Your doctor will ask questions about your history of:

  • symptoms that suggest stomach cancer
  • Helicobacter pylori (H. pylori) infection
  • stomach problems, such as polyps in the stomach or gastritis
  • stomach surgery

Your doctor may also ask about a family history of:

  • stomach cancer
  • risks for stomach cancer
  • other gastrointestinal (GI) cancers

A physical exam allows your doctor to look for any signs of stomach cancer. During a physical exam, your doctor may:

  • feel the abdomen for enlarged organs, lumps or swelling
  • check for swollen lymph nodes in the armpits and around the collarbones
  • do a digital rectal exam

Find out more about physical exam.

Complete blood count (CBC)

A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. A CBC may be done to check for anemia from long-term (chronic) bleeding.

Find out more about a complete blood count (CBC).

Blood chemistry tests

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are working and can help find abnormalities. Blood chemistry tests used to stage stomach cancer include the following.

Liver function tests check how well the liver is working. High levels of certain chemicals may mean that the cancer has spread to the liver.

Kidney function tests check how well the kidneys are working. High levels of certain chemicals may mean that the cancer has spread to the ureters or kidneys.

An electrolyte panel checks levels of electrolytes in the body and can show how the kidneys are working. Abnormal levels of electrolytes (an electrolyte imbalance) may mean there is not the right amount of fluids in the body for it to work properly.

Find out more about blood chemistry tests.

Upper gastrointestinal (GI) endoscopy

An upper gastrointestinal (GI) endoscopy is the most common test used to diagnose stomach cancer. During an upper GI endoscopy, the doctor looks inside the esophagus, stomach and first part of the small intestine (duodenum) using a flexible tube with a light and lens on the end (called an endoscope). This test is also called an esophagogastroduodenoscopy (EGD). It can also be called a gastroscopy when only the stomach is examined.

An upper GI endoscopy is done to check the stomach for bleeding, ulcers, polyps, tumours and inflammation (gastritis). A biopsy sample may be collected during an upper GI endoscopy.

An endoscopic ultrasound (EUS) uses a small ultrasound probe on the end of the endoscope to make images of parts of the body. It is often done during the same time as an upper GI endoscopy. An EUS is used to find out how deep a tumour has grown into the wall of the stomach. It is also used to check if cancer has spread to nearby lymph nodes and areas. Doctors can use an EUS to guide a biopsy needle to a specific area in the body (called an EUS-guided needle biopsy).

Find out more about an endoscopy and ultrasound.


During a biopsy, the doctor removes tissues or cells from the body so they can be tested in a lab. A report from a pathologist will show whether or not cancer cells are found in the sample. If cancer is found, the pathologist will also find out the type of cancer and the grade.

An endoscopic biopsy removes small tumours and biopsy samples from the stomach during an endoscopy. It is usually done during an upper GI endoscopy.

An EUS-guided needle biopsy uses an EUS to guide a biopsy needle to a specific area. It may be used to check for cancer deep within the stomach wall.

A laparoscopic biopsy removes tissue using a special tool on a thin, flexible lighted tube called a laparoscope. It is usually done after a diagnosis of stomach cancer. It may be used to look for cancer that has spread outside of the stomach such as to the peritoneum or lymph nodes.

Find out more about a biopsy.

Tumour marker tests

Tumour markers are substances found in the blood, tissues or fluids removed from the body. An abnormal amount of a tumour marker may mean that a person has stomach cancer. Tumour markers can also be used to plan and check your response to cancer treatment.

The following tumour markers may be measured for stomach cancer.

HER2 is a gene that controls a protein on cells that helps them grow. If the HER2 gene changes (mutates) and makes too much of this protein, it may help a tumour grow. HER2 status testing is done on tissue of advanced stomach cancers to find out if the cancer makes too much of the HER2 protein (called HER2-positive stomach cancer). Knowing the HER2 status can help doctors plan your treatment. Find out more about HER2 status tests.

Carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9) or cancer antigen 125 (CA125) levels in the blood may be higher than normal if there is a stomach tumour.

Find about more about tumour markers.

CT scan

A computed tomography (CT) scan uses special x-ray equipment to make 3D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. Before the CT scan, a dye (called a contrast medium) may be given by mouth or injected into a vein (given intravenously). This can help the doctor see the body parts better.

CT scans of the chest, abdomen and pelvis are used to check if stomach cancer has spread to other organs, such as the lungs or liver. A CT scan can also check if the cancer has spread to lymph nodes around the stomach that were not seen during an endoscopic ultrasound.

Doctors can also use a CT scan to guide a biopsy needle to a specific area in the body. This is called a CT-guided biopsy.

Find out more about a CT scan.

Chest x-ray

A chest x-ray uses small doses of radiation to make an image of the chest on film. It is used to check if stomach cancer has spread to the lungs. It is not needed if you had a CT scan of the chest.

Find out more about an x-ray.


Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3D pictures.

An MRI of the abdomen may be used to get a closer look at tumours that were found in the liver with a CT scan. It is used to check if stomach cancer has spread to the liver.

Find out more about an MRI.

PET scan

A positron emission tomography (PET) scan uses radioactive materials called radiopharmaceuticals to look for changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3D colour images of the area being scanned.,

A PET scan is used to look for cancer that has spread outside of the stomach. Sometimes a PET scan may be done at the same time as a CT scan (called a PET-CT scan).

Find out more about a PET scan.


A laparoscopy is surgery that uses a laparoscope (a type of endoscope) to examine or remove internal organs through several small surgical cuts (incisions) in the skin. The laparoscope has a camera on the end that sends live video to a TV screen. It may be used to stage stomach cancer and to help doctors plan your treatment. A laparoscopy is used to:

  • check the outside of the stomach (called the serosa) and nearby lymph nodes for cancer
  • look for cancer in other parts of the abdomen, such as the peritoneum or the liver, that a CT scan or an ultrasound may have missed
  • take a biopsy (laparoscopic biopsy)
  • remove fluid (peritoneal washings) from the abdomen to look for cancer cells

A laparoscopy may be used with an ultrasound to help find hidden areas that contain cancer.

Questions to ask your healthcare team

To make the decisions that are right for you, ask your healthcare team questions about diagnosis.

Expert review and references

  • Ashley Stueck, MD, FRCPC
  • American Cancer Society . Stomach Cancer Early Detection, Diagnosis and Staging . 2014 : https://www.cancer.org/.
  • American Society of Clinical Oncology (ASCO) . Cancer.Net: Stomach Cancer. 2020: https://www.cancer.net/.
  • Avital I, Nissan A, Golan T, Lawrence YL, Stojadinovic A. Cancer of the stomach. DeVita VT Jr, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, PA: Wolters Kluwer; 2018: 53:762–796.
  • National Comprehensive Cancer Network . NCCN Clinical Practice Guidelines in Oncology: Gastric Cancer (Version 1.2019). https://www.nccn.org/home.

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

We do our best to make sure that the information we provide is accurate and reliable but cannot guarantee that it is error-free or complete.

The Canadian Cancer Society is not responsible for the quality of the information or services provided by other organizations and mentioned on cancer.ca, nor do we endorse any service, product, treatment or therapy.

1-888-939-3333 | cancer.ca | © 2024 Canadian Cancer Society