The organ is about 20 feet long and consists of three sections: the duodenum; jejunum; and ileum. The duodenum is the first part of the small intestine and runs from the pylorus, the opening from the stomach, into the intestinal tract. The jejunum starts after the duodenum and comprises two-fifths of the organ. The ileum is the last section of the small intestine and leads to the large intestine.

Cancer of the small intestine is rare. About 4,700 cases occur annually in the United States, and approximately 1,200 people die each year from of the disease. Small-intestine cancer includes adenocarcinoma, lymphoma (non-Hodgkin's), sarcoma and carcinoid tumors. These growths only account for 1 to 2 percent of all gastrointestinal (digestive system) cancers.

This summary addresses each of these cancer types. For more details on lymphoma and sarcoma, see the corresponding summaries. A detailed description of gastrointestinal carcinoids appears within this summary.