Small Intestine Cancer Facts

November 22, 2024

This page was reviewed under our medical and editorial policy by Laleh Melstrom, M.D., M.S., associate professor of surgery and immuno-oncology, Division of Surgical Oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

Small intestine cancers are rare. Approximately 13,920 people will receive a small intestine cancer diagnosis in the United States in 2025, according to the American Cancer Society.

What Is Small Intestine Cancer?

The small intestine (also called the small bowel) is part of the digestive tract, carrying digested food from the stomach to the colon (also called the large intestine). The small bowel is a long tube approximately 20 feet in length with three distinct parts: the duodenum, the jejunum and the ileum.

When cancer develops in this part of the gastrointestinal tract, it’s referred to as small intestine cancer.

Cancers are most likely to develop in the first part of the small bowel (the duodenum), but this disease may also affect the jejunum and ileum.

What Causes Small Intestine Cancer?

Small intestine cancer is caused by DNA changes in cells that multiply and grow out of control, crowding out healthy cells. Researchers have not pinpointed a specific cause for these genetic changes, but there are risk factors that increase the likelihood of being diagnosed with this condition.

What Increases the Risk of Small Intestine Cancer?

Factors that put patients at higher risk for developing small intestine cancer are called risk factors. A patient’s risk of being diagnosed with small intestine cancer depends on a complex interaction between lifestyle factors and inherited risks — in other words, the ones people are born with.

Risk factors for small intestine cancer include:

• Age: Advancing age increases the risk for developing small intestine cancer.
• Sex: Being male increases the risk for developing small intestine cancer.
• Race: Being African-American increases risk of small bowel cancer.
• Smoking and drinking alcohol excessively are believed to increase the risk of this cancer type.
• Having had colon cancer increases risk of developing small intestine cancer.
• History of certain conditions: Having a history of Crohn’s disease or celiac disease may increase the risk of small intestine cancer.

Is Small Intestine Cancer Hereditary?

Some risk factors that raise the risk for developing small intestine cancer may be inherited from a parent or other family member.

Inherited risks for small intestine cancer include familial adenomatous polyposis, Peutz-Jeghers syndrome, MUTYH-associated polyposis, hereditary nonpolyposis colorectal cancer and cystic fibrosis.

Types of Small Intestine Cancer

There are five types of small intestine cancer that differ depending on the type of cell affected including:

• Adenocarcinoma is the most common type of small intestine cancer; it starts in the cells that make the mucus lining on the inside of the small intestine and most often develops at the junction of the small intestine and the stomach.
• Leiomyosarcomas are rare cancers that start in smooth muscle cells in the wall of the small intestine, most often appearing near the large intestine.
• Carcinoid tumors start in hormone-making cells in the intestine.
• Gastrointestinal stromal tumors (GISTs) start in special cells found in the wall of the GI tract, called the interstitial cells of Cajal.
• Lymphomas are a type of cancer that typically start in immune system cells, but can also start in intestinal organs.