What Is a Small Intestine Cancer?

The gastrointestinal (digestive) system

The digestive system processes food for energy and rids your body of solid waste. After you chew and swallow your food, it enters the esophagus. This is a tube-shaped organ that carries food to your stomach. The esophagus joins the stomach just beneath the breathing muscle under the lungs (the diaphragm)

The stomach is a sack-like organ that holds swallowed food and begins the digestive process by secreting gastric juice. The food and gastric juices are mixed into a thick fluid, which is then emptied into the small intestine. The small intestine continues breaking down the food and absorbs most of the nutrients. Even though it is called the small intestine, it is actually the longest section of the gastrointestinal (GI) tract. The small intestine is about 15 to 20 feet long. Because of its length, to fit in the abdomen, the small intestine has many loops.

The small intestine has 3 sections. The first section is the duodenum. It is short, only about 8 inches long. It is directly attached to the stomach and is where the stomach empties its contents. A short distance from where it attaches to the stomach, the pancreatic duct and bile duct attach to the duodenum. These discharge bile and pancreatic juices into the duodenum to further the digestive process. They attach at a site called the ampulla of Vater

The next 2 sections of the small intestine are the jejunum and ileum. These parts of the intestine are where all the nutrients in food are absorbed into the bloodstream. They make up most of the length of the small intestine with the ileum being slightly longer. The duodenum goes into the jejunum. The ileum comes after the jejunum and ends when it empties into the large intestine (colon). The colon is a muscular tube about 4 to 5 feet long. The appendix is found near the place the ileum meets the colon. The colon continues to absorb water and mineral nutrients from the food matter and serves as a storage place for waste. The waste left after this process goes into the rectum. From there it passes out of your body through the anus.

illustration of the digestive system showing the liver, gallbladder, ascending colon, small intestine, cecum, appendix, rectum, esophagus, stomach, transverse colon, descending colon, sigmoid colon and anus

Small intestine cancers

Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

Types of small intestine cancers

These major types make up about 60% to 70% of small intestine cancers:

This document is about the 4th major type of small intestinal cancer – adenocarcinoma.

Adenocarcinomas make up about 30% to 40% of small intestine cancers. This type of cancer starts from the cells that line the intestine. Most experts think that cancer of the small intestine develops much like colorectal cancer. It first begins as a small benign outgrowth called a polyp. Over time, the polyp can change into a cancer. Most small intestinal cancers develop in the duodenum and the rest occur in the jejunum and ileum.

A major site of cancer in the duodenum is the ampulla of Vater. But because this area is closely associated with the pancreas, it is treated like pancreatic cancer and discussed in Pancreatic Cancer

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: April 30, 2014 Last Revised: February 9, 2016

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