What is stomach cancer?

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Stomach cancer (sometimes called gastric cancer) starts in the cells of the stomach. A cancerous (malignant) tumour is a group of cancer cells that can grow into nearby tissue and destroy it. The tumour can also spread (metastasize) to other parts of the body.

The stomach is part of the digestive system. It is a muscular, J-shaped organ in the abdomen that holds and breaks down food.

Diagram of the digestive system
Diagram of the digestive system

Cells in the stomach sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) tumours such as gastric polyps.

Changes to cells of the stomach can also cause precancerous conditions. This means that the abnormal cells are not yet cancer, but there is a chance that they may become cancer if they aren't treated. The most common precancerous conditions of the stomach are gastric epithelial dysplasia and gastric adenomas.

But in some cases, changes to stomach cells can cause stomach cancer. Most often, stomach cancer starts in the gland cells that line the inside of the stomach. This type of cancer is called adenocarcinoma of the stomach and makes up about 95% of all stomach cancer cases.

Rare types of stomach cancer can also develop. These include gastrointestinal stromal tumours (GISTs) and lymphomas.

The stomach

Stomach cancer starts in stomach cells. The stomach is part of the digestive system and breaks down food.

Cancerous tumours of the stomach

Adenocarcinoma is the most common type of stomach cancer. There are also rare types of stomach tumours.

Precancerous conditions of the stomach

Precancerous stomach conditions are changes to cells that make them more likely to develop into cancer.

Non-cancerous tumours of the stomach

Gastric polyps are the most common non-cancerous stomach tumours. Other non-cancerous stomach tumours are rare.