What is stomach 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 food pipe (oesophagus) and the other end is joined to the bowel. 

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

• top (fundus)

• middle (body) 

• bottom (antrum or pylorus) 

The cardia is the entrance to the stomach and the pylorus is the exit into the duodenum (top part of the small bowel).

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 duodenum (the top part of the small bowel)

How does the stomach work?

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 gastric juice which mixes with the food, so it is easy to digest.

Glands in the inner lining of the stomach make gastric juice. It contains stomach acid, water and a protein called pepsin. It begins to flow as soon as we smell something. The stomach muscle contracts, churning the food with the juice, which changes it to a thick liquid. It takes a couple of hours for this to happen. Then the liquid moves into the bowel where the body absorbs it.

The stomach continues to produce gastric juice and hormones, even when it’s empty. It also produces a thick mucus to protect the lining of the stomach from the acid and pepsin.

Where does stomach cancer start?

The stomach wall is made up of a number of layers. These are:

• outer lining

• muscle layer

• supportive tissue

• inner lining

Cancer can start in any part of the stomach wall. Your treatment depends on where in the stomach the cancer starts and what type of cell it starts in.

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

Some cancers can start in the cells that help food move through the digestive system. 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-Hodgkin lymphoma. MALT lymphoma of the stomach is often linked to a chronic stomach infection caused by the bacteria Helicobacter pylori.

Read about MALT lymphoma

Neuroendocrine cancers (NECs) start in the hormone cells in the stomach.

Find out more about the different types of stomach cancer

How common is stomach cancer?

Around 6,600 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 (H. pylori). But not everyone with H. pylori will develop stomach cancer.

Go to information about risks and causes of stomach cancer