Cancerous tumours of the stomach

A cancerous tumour of the stomach can grow into nearby tissue and destroy it. The tumour can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant or invasive tumours.

Most stomach cancers develop in the lower and middle parts of the stomach.

Adenocarcinoma is the most common type of stomach cancer. It makes up about 95% of all stomach cancer cases. It starts in the gland cells that line the inside of the stomach (the lining is called the mucosa).

Adenocarcinoma of the stomach may also be called gastric cancer.

There are 2 main types of adenocarcinoma of the stomach.

Intestinal adenocarcinoma is often well differentiated. This means that the cells are abnormal but they can look a lot like normal cells. They tend to be arranged in a pattern that looks like tubes. Intestinal adenocarcinoma usually starts from a Helicobacter pylori (H. pylori) infection. It may also be called tubular, papillary or mucinous adenocarcinoma because of how the cells look under a microscope.

Diffuse adenocarcinoma (also called poorly cohesive adenocarcinoma) is undifferentiated or poorly differentiated. This means that the cells don't look or behave like normal cells. Cancer cells are scattered throughout the stomach lining. Diffuse adenocarcinoma is more common in younger people and may lead to linitis plastica (a condition where the stomach wall becomes hard and leathery). Signet ring cell carcinoma is a type of diffuse adenocarcinoma.

Other, less common types of adenocarcinoma include:

• mixed adenocarcinoma (made up of both intestinal and diffuse adenocarcinoma)
• hepatoid adenocarcinoma
• gastric lymphoepithelioma-like carcinoma

The following cancerous tumours of the stomach are rare.

Gastrointestinal stromal tumours (GISTs) start in special cells of the gastrointestinal (GI) tract called interstitial cells of Cajal. GISTs can happen anywhere in the GI tract, but they develop most often in the stomach. GISTs can be non-cancerous (benign) or cancerous. A cancerous GIST is usually treated with surgery or targeted therapy drugs such as imatinib (Gleevec). Find out more about gastrointestinal stromal tumours (GISTs).

Neuroendocrine tumours (NETs) start in the cells of the neuroendocrine system and can develop in organs of the GI tract, including the stomach. These types of tumours are called gastrointestinal neuroendocrine tumours (GI NETs) and tend to grow slowly. GI NETs are often treated with surgery and drugs called somatostatin analogues. Find out more about neuroendocrine tumours (NETs).

Lymphomas can start in the lymphatic tissue of the stomach's inner lining (called the mucosa). A type of lymphoma that commonly starts in the stomach is called mucosa-associated lymphatic tissue (MALT) lymphoma. Most MALT lymphomas of the stomach are caused by an H. pylori infection. Treatment for MALT lymphoma of the stomach often includes antibiotics and proton-pump inhibitors.

Adenosquamous carcinoma is a mixture of both adenocarcinoma and squamous cell carcinoma. It tends to have a less favourable prognosis than adenocarcinoma.