Overview of Gastrointestinal (GI) Cancers
Gastrointestinal (GI) cancer is a term used for the group of cancers that affect the gastrointestinal tract and other organs that are contained within the digestive system, including the esophagus, pancreas, stomach, colon, rectum, anus, liver, biliary system, and small intestine.
Common Types of Gastrointestinal Cancers
Colorectal cancer starts in the colon or the rectum. These two cancers are often grouped together because they share many similar features. Most colorectal cancers begin as small, noncancerous (benign) clumps of cells, called polyps, on the inner lining of the colon or rectum. Regular screening is recommended for prevention since polyps don’t usually produce symptoms.
Liver cancer starts in the cells of the liver. The liver, which is the largest internal organ, lies in the upper right portion of your abdomen, beneath your diaphragm and above your stomach. While other cancers can affect the liver, only cancers that actually start in the liver are considered liver cancer (called primary liver cancer). Hepatocellular carcinoma, which begins in the main type of liver cell (hepatocyte), is the most common type of liver cancer.
Stomach cancer, also called gastric cancer, starts in the stomach. While stomach cancer can develop anywhere in the organ, most stomach cancers develop in the mucus-producing cells of the stomach’s inner lining. These cancers are called adenocarcinomas.
Cancer that begins in the tissues of the pancreas -- an organ that sits behind the stomach. It releases enzymes that help digest foods (especially fats) and hormones that help control blood sugar levels. The pancreas has two types of cells--exocrine and endocrine--which form different types of tumors.
A cancer that occurs in the esophagus -- a hollow, muscular tube that connects the throat to the stomach. It is located behind the trachea (windpipe) and in front of the spine. The esophagus helps move the food you swallow from the back of the throat to the stomach for digestion.
Other Types of GI Cancers
Anal cancer starts in the anal canal--a short tube at the end of your rectum through which stool leaves your body. The inner lining of the anal canal is the mucosa. Most anal cancers start from cells in the mucosa. Anal cancers that start from cells in the glands located under the mucosa are called adenocarcinomas. Many types of tumors can develop in the anus, including non-cancerous ones.
Small Intestine Cancer
Small intestine, also called small bowel cancer, occurs in the small intestine--a long tube that carries digested food between the stomach and the large intestine (colon). Because the small intestine is made up of many different types of cells, different types of cancer can start there. There are four major types of small intestine cancers, which include adenocarcinomas, carcinoid tumors, lymphomas, and sarcomas. Small intestine cancer often begins with non-cancerous polyps, which over time, can change into cancer.
Gastrointestinal Stromal Tumors (GIST)
GISTs start in special cells, called interstitial cells of Cajal (ICCs), located in the wall of the gastrointestinal (GI) tract, also known as the digestive tract. ICC cells are part of the autonomic nervous system--the part of the nervous system that regulates body processes such as digesting food. The most common sites for GISTs are the stomach and small intestine.
Gallbladder & Biliary Tract Cancer
Gallbladder cancer occurs when malignant cancer cells form in the tissues of the gallbladder. The gallbladder is a small, pear-shaped organ located next to the liver. Its role is to store bile, a fluid that aids with digestion and fat absorption in the small intestine. Biliary tract cancer (also known as cholangiocarcinoma) is cancer that occurs in the bile ducts (tubes that transport bile from the liver). Biliary tract cancer can form anywhere along the bile ducts.