Small Bowel Cancer: Introduction

Approved by the Cancer.Net Editorial Board, 04/2022

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Small Bowel Cancer, also called small intestine cancer. Use the menu to see other pages. Think of that menu as a roadmap for this entire guide.

About the small bowel

The small bowel is part of the digestive system. It breaks down food and nutrients to be absorbed into the body. The small bowel is also called the small intestine. It links the stomach to the large intestine, which is called the colon. The small bowel is divided into 3 parts:

  • The duodenum. The part closest to the stomach.

  • The jejunum. The middle portion.

  • The ileum. The bottom section, which connects to the large intestine, or colon.

The small bowel is approximately 15 feet long, folds many times to fit inside the abdomen, and makes up about 3/4 of the digestive system.

Small bowel cancer

Small bowel cancer starts when healthy cells in the lining of the small bowel change and grow out of control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread. Cell changes can take a long time to develop. Both genetic and environmental factors can cause such changes, although the specific causes of small bowel cancer are generally not well understood.

Types of small bowel cancer

There are 5 main types of small bowel cancer:

  • Adenocarcinoma. Adenocarcinoma is the most common type of small bowel cancer, usually occurring in the duodenum or jejunum. Adenocarcinoma begins in the gland cells of the small bowel. This guide focuses on this type of small bowel cancer.

  • Sarcoma. Small bowel sarcoma is generally a leiomyosarcoma, which is a tumor that arises in the muscle tissue that makes up part of the intestine. This type of tumor most often occurs in the ileum. Learn more about sarcoma.

  • Gastrointestinal stromal tumor (GIST). GIST is an uncommon tumor that is believed to start in cells found in the walls of the gastrointestinal (GI) tract, called interstitial cells of Cajal (ICC). GIST belongs to a group of cancers called soft-tissue sarcomas. Learn more about gastrointestinal stromal tumors.

  • Neuroendocrine tumor. Neuroendocrine tumors start in the hormone-producing cells of various organs and generally occur in the ileum. These may also be called a carcinoid tumor. Learn more about neuroendocrine tumors.

  • Lymphoma. Lymphoma is a cancer of the lymph system, which is part of the body’s immune system. Lymphoma that occurs in the small bowel usually occurs in the jejunum or ileum and is most commonly non-Hodgkin lymphoma. Learn more about non-Hodgkin lymphoma.

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with small bowel cancer and general survival rates. Use the menu to choose a different section to read in this guide.