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What is stomach cancer?

Stomach cancer is cancer that starts anywhere inside the stomach or the stomach wall. It’s also called gastric cancer.

The stomach

The stomach is part of the digestive system. It's in the upper left side of the tummy (abdomen). The top of the stomach joins the bottom of the foodpipe (oesophagus) and the other end is joined to the bowel. 

Diagram of the stomach

It is a muscular bag that has three main parts. They are the:

  • top (fundus)
  • middle (body) 
  • bottom (antrum or pylorus) 

At each end of the stomach there is a valve called a sphincter. These valves control the movement of food through the digestive system.

They are the:

  • cardiac sphincter - at the top joining the oesophagus to the stomach
  • pyloric sphincter - which is at the bottom joining the stomach to the bowel
Diagram of the sphincter

How the stomach works

Food passes from the oesophagus into the stomach. The stomach then stores the food and breaks it down (digests it) so our body can absorb it. It does this by producing juices and mixing the food up with them so it is easily digestible.

Glands in the wall of the stomach make the juices. These juices are stomach acid and a protein called pepsin. They begin to flow as soon as we smell something. 

The muscle wall of the stomach contracts, churning the food with the juices, which changes it to a thick liquid. It takes a couple of hours for this to happen and then it moves into the bowel where the body absorbs it.

Even when it is empty, the stomach continues to produce juices and hormones. So, to protect the lining of the stomach from the acid and pepsin it also produces a thick mucus.

Where stomach cancer starts

Diagram showing how the stomach works

Cancer can start in any part of the stomach or the stomach wall. Your treatment depends on where in the stomach the cancer starts.

Most stomach cancers start in the gland cells in the inner stomach lining. These are called adenocarcinomas.

Stomach cancer can start in the wall of the stomach. These are called gastrointestinal stromal tumours (GIST) and are a type of soft tissue sarcoma.

Some cancers can also start in immune system cells in the stomach. These are called non Hodgkins lymphoma.

Or they can start in the hormone cells in the stomach. These are called neuroendocrine cancers.

How common is stomach cancer?

Around 6,700 people are diagnosed with stomach cancer in the UK each year. The number of people in the UK diagnosed with stomach cancer has fallen since the early 1990s. 

Who gets stomach cancer?

Stomach cancer is more common in older people. Around 50 out of 100 cases (around 50%) occur in people aged 75 or over.

It is more common in men than women.

Many stomach cancers are linked to lifestyle or environmental factors, including diet. Stomach cancer is linked with a bacteria that lives in the stomach called Helicobacter pylori. But not everyone with Helicobacter pylori will develop stomach cancer.

Last reviewed: 
15 Aug 2019
  • Cancer Incidence from Cancer Intelligence Statistical Information Team at Cancer Research UK  (2015 - 2017 UK average) 
    Accessed September 2020

  • Gastric cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up 
    E Smyth and others, 
    Annals of Oncology, 2016. Volume 27, Pages v38–v49

  • Anatomy and Physiology in Health and Illness (11th edition)
    Ross and Wilson
    Churchill Livingstone, 2010

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2014