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Stomach Cancer: Introduction

What is cancer?

Cancer is when cells in the body change and grow out of control. To help you understand what happens when you have cancer, let's look at how your body works normally. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body doesn't need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).

What is stomach cancer?

Stomach cancer is a disease in which cancer starts in cells in the stomach. It’s also called gastric cancer. There are different types of stomach cancer. They each grow in different parts of the stomach. The different types of cancer cells also look different.

The most common type of stomach cancer is called adenocarcinoma. This type forms in the inner layer of the stomach. The inner layer of the stomach is called the mucosa.

Other types of stomach cancer are much less common and include:

  • Lymphomas. These are cancers of immune system tissue.

  • Gastrointestinal stromal tumors (GIST).  This is a rare cancer of the gastrointestinal (GI) tract, also called the digestive tract. GIST starts in cells in the stomach wall called the interstitial cells of Cajal.

  • Carcinoid tumors (neuroendocrine tumors). These come from cells in the stomach that make hormones.

Understanding the stomach

The stomach is part of the digestive tract or gastrointestinal system. It's a curved sac that holds and starts to digest food so it can be used by the body. It empties into the small intestine. The stomach is made of different layers. The mucosa is the innermost layer. It makes stomach acid and some of the enzymes that digest food. Most stomach cancers start in the mucosa. There’s also a thick muscle layer that helps mix up food. It's important to know how far the cancer has spread into the layers of the stomach. 

Talk with your healthcare provider

If you have questions about stomach cancer, talk with your healthcare provider. They can help you understand more about this cancer.