Understand What is Cancer?

An uncontrolled growth of cells in our body is cancer. If we are injured or hurt, the body typically begins to divide and make cells to help heal. However, sometimes, the body forgets that it must stop creating more cells, leading to cancer.

stomach cancer

What is a stomach?

The stomach is a sac-like organ that’s an essential part of the digestive system.

After food is chewed and swallowed, it enters the esophagus, a tube that carries food through the throat and chest to the stomach. The esophagus joins the stomach at the gastroesophageal (GE) junction, just beneath the diaphragm (the thin sheet of breathing muscle under the lungs). The stomach then starts to digest the food by secreting gastric juice. The food and gastric juice are mixed and then emptied into the first part of the small intestine called the duodenum.

The stomach is divided into 5 parts.

The first 3 parts make up the proximal stomach:

  • Cardia: the first part, which is closest to the esophagus
  • Fundus: the upper part of the stomach next to the cardia
  • Body: the central part of the stomach, between the upper and lower parts

The lower 2 parts make up the distal stomach:

  • Antrum: the lower portion (near the small intestine), where the food mixes with gastric juice
  • Pylorus: the last part of the stomach, which acts as a valve to control emptying of the stomach contents into the small intestine.

Stomach cancer can happen in any part of the stomach. In most of the world, stomach cancers occur in the body of the stomach. 

stomach cancer

Development of stomach cancer

Stomach cancers tend to develop slowly over many years. Before a true cancer develops, pre-cancerous changes often occur in the stomach’s inner lining (mucosa). These early changes rarely cause symptoms, so they often go undetected.

Cancers starting in different sections of the stomach can cause various symptoms and tend to have different outcomes. The cancer’s location can also affect treatment options. For example, cancers that start at or grow into the GE junction are usually staged and treated like esophagus cancers.

Types of stomach cancer


Most stomach cancers (about 90% to 95%) are adenocarcinomas. These cancers develop from the gland cells in the innermost lining of the stomach. 

If you are told you have stomach cancer (or gastric cancer), it will almost always be an adenocarcinoma. 

Gastrointestinal stromal tumors (GISTs)

These uncommon tumours start in very early forms of cells in the wall of the stomach called interstitial cells of Cajal. Some GISTs are much more likely to grow into other areas or spread to other body parts. Although GISTs can start anywhere in the digestive tract, most start in the stomach. 

Neuroendocrine tumours (including carcinoids)

Neuroendocrine tumours (NETs) start in cells in the stomach (or other parts of the digestive tract) that act like nerve cells in some ways and like hormone-making (endocrine) cells in others. Most NETs grow slowly and do not spread to other organs, but some can grow and spread quickly. NETs are discussed in more detail in 


These cancers start in immune system cells called lymphocytes. Lymphomas usually begin in other body parts, but some can start in the stomach wall. The treatment and outlook for these cancers depend on the type of lymphoma and other factors.

Other types of cancer, such as squamous cell carcinomas, small cell carcinomas, and leiomyosarcomas, can also start in the stomach, but these cancers are sporadic.

stomach cancer

Symptoms stomach cancer

Signs and symptoms of stomach cancer may include

  • Trouble swallowing
  • Belly pain
  • Feeling bloated after eating
  • Feeling full after eating small amounts of food
  • Not feeling hungry when you would expect to be hungry
  • Heartburn
  • Indigestion
  • Nausea
  • Vomiting
  • Losing weight without trying
  • Feeling very tired
  • Stools that look black

Stomach cancer doesn’t always cause symptoms in its early stages. When they happen, symptoms might include indigestion and pain in the upper part of the belly. Symptoms might not occur until the cancer is advanced. Later stages of stomach cancer might cause symptoms such as feeling tired, losing weight without trying, vomiting blood and having black stools.

Stomach Cancer Causes 

It’s not clear what causes stomach cancer. Experts believe most stomach cancers start when something hurts the inside lining of the stomach. Examples include stomach infection, especially with a bacteria called Helicobacter Pylori or H pylori. They are having long-standing acid reflux and eating a lot of salty foods. Not everyone with these risk factors gets stomach cancer, though. So, more research is needed to find out exactly what causes it.

Stomach Cancer Risk factors

Factors that increase the risk of stomach cancer include:

  • Ongoing problems with stomach acid backing up into the esophagus, which is called gastroesophageal reflux disease
  • A diet high in salty and smoked foods
  • A diet low in fruits and vegetables
  • Infection in the stomach caused by a germ called Helicobacter pylori
  • Swelling and irritation of the inside of the stomach, which is called gastritis
  • Smoking
  • Growths of noncancerous cells in the stomach, called polyps
  • Family history of stomach cancer

stomach cancer

Stomach Cancer Diagnosis

Medical history, physical exam, and tests to look for bleeding
Medical history of symptoms (such as eating problems, pain, bloating, etc.) and possible risk factors might suggest stomach cancer or another cause.
Blood tests to look for anemia (a low red blood cell count) could be caused by the cancer bleeding into the stomach. A stool test to look for occult bleeding can be done.
If suspicion is high, the patient is referred to a gastroenterologist

  • Upper endoscopy

Upper endoscopy (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, 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 the first part of the small intestine. Biopsy samples can be removed using instruments passed through the endoscope if abnormal areas are seen. The tissue samples are sent to a lab, where they are examined with a microscope to see if they contain cancer.

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

Endoscopy can also be used as part of a particular imaging test known as endoscopic ultrasound.

  • Biopsy

If an abnormal-looking area is seen on endoscopy or an imaging test, the only way to tell if it’s cancer is by doing a biopsy. The doctor removes small pieces (samples) of the abnormal area during a biopsy.

  • 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 several reasons, including:

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

  • Endoscopic ultrasound

Endoscopic ultrasound (EUS) is often used to see how far a cancer might have spread into the stomach wall or nearby areas or 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 examination is put up against the stomach wall 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, the nearby lymph nodes and other structures just outside the stomach. 

EUS can also 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 helpful 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.

Stomach Cancer Treatment

Surgery: Where cancer starts in the stomach is one-factor health care providers consider when making a treatment plan. Other factors might include the cancer’s stage and the type of cells involved. Treatment often includes surgery to remove the stomach cancer. Other treatments may be used before and after surgery.

Other treatment options include chemotherapy, targeted therapy or radiation.

Stomach Cancer Prevention

To lower the risk of stomach cancer, you can

  • Eat plenty of fruits and vegetables. Try to include fruits and vegetables in your diet each day. Choose a variety of colourful fruits and vegetables.
  • Reduce the amount of salty and smoked foods you eat. Protect your stomach by limiting these foods.
  • Stop smoking. If you smoke, quit. If you don’t smoke, don’t start. Smoking increases your risk of stomach cancer and many other types of cancer. Quitting smoking can be difficult, so ask your healthcare provider for help.
  • Tell your healthcare provider if stomach cancer runs in your family. People with a strong family history of stomach cancer might have stomach cancer screening. Screening tests can detect stomach cancer before it causes symptoms.