What is stomach cancer?

Stomach cancer is a malignant tumour that starts in cells of the stomach. Malignant means that it is a cancerous tumour that can spread, or metastasize, to other parts of the body.

The stomach is part of the digestive system. It is a muscular, sac-like organ in the upper abdomen. In the stomach, the food is mixed with digestive juices. These juices are made by glands in the lining of the stomach. They help break the food down into a semi-solid mixture that then passes into the small intestine.

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

Changes to cells in the stomach can also cause precancerous conditions. This means that the cells are not yet cancer, but there is a chance that they may become cancer if they aren’t treated. Precancerous conditions that can develop in the stomach are gastric adenoma, or adenomatous polyps, and gastric epithelial dysplasia.

In some cases, changes to stomach cells can cause cancer. Most often, cancer starts in gland cells in the inner layer of the stomach wall, which is called the gastric mucosa. This type of cancer is called adenocarcinoma of the stomach. It makes up about 95% of all stomach cancers.

Rare types of stomach cancer can also develop. These include gastric non-Hodgkin lymphomas and soft tissue sarcomas.

Diagram of the digestive system
Diagram of the digestive system

Expert review and references

  • American Cancer Society. Stomach Cancer. Atlanta, GA: American Cancer Society; 2014: http://www.cancer.org/acs/groups/cid/documents/webcontent/003141-pdf.pdf.
  • Avital, I. et al . Cancer of the stomach. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles & Practice of Oncology. 9th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011: 80: pp. 924-954.
  • Bosman FT, Carneiro F, Hruban RH, Theise ND. WHO Classification of Tumours of the Digestive System. 4th ed. Lyon: International Agency for Research on Cancer (IARC); 2010.
  • Martini FH, Timmons MJ, Tallitsch RB. Human Anatomy. 7th ed. San Francisco: Pearson Benjamin Cummings; 2012.
  • National Cancer Institute. Gastric Cancer Treatment (PDQ®) Patient Version. Bethesda, MD: National Cancer Institute; 2014.
  • Popa E, Scnoll-Sussman F, Jesudian A, et al . Uncommon tumours of the stomach. Raghavan D, Blanke CD, Honson DH, et al. (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 28: 389-408.
  • Young B, O'Dowd G, Woodford P (eds.). Wheaters's Functional Histology. 6th ed. Churchill Livingston; 2014.

Anatomy and physiology of the stomach

The stomach is a muscular, sac-like organ in the upper abdomen. It is part of the digestive system. Learn about the anatomy and physiology of the stomach.

Cancerous tumours of the stomach

The most common type of stomach cancer is adenocarcinoma. Learn about cancerous tumours of the stomach.

Precancerous conditions of the stomach

Precancerous conditions of the stomach may develop into stomach cancer if left untreated. Learn about precancerous conditions of the stomach.

Non-cancerous tumours of the stomach

Gastric polyps are non-cancerous tumours of the stomach. Learn about non-cancerous tumours of the stomach.