- Adenocarcinoma is the type of cancer cell found in 90 to 95 percent of colon cancer cases. Adenocarcinoma forms from the cells that help produce the mucus that lines the colon or rectum. They can invade the wall of the colon and then spread via lymphatic channels to surrounding lymph nodes. From there they can spread to the liver and the lungs.
- Carcinoid tumors and neuroendocrine tumors typically occur in the small intestine and appendix and occasionally the rectum. They rarely occur in the colon.
- Gastrointestinal stromal tumors can form anywhere in the digestive tract, though rarely in the colon. They can start in the special cells found in the wall of the GI tract, called the interstitial cells of Cajal (ICCs). ICCs are cells of the autonomic nervous system, the part of the nervous system that regulates body processes such as digesting food. ICCs are sometimes called the “pacemakers” of the GI tract because they signal the muscles in the digestive system to contract to move food and liquid through the GI tract. That’s why it’s important to have your gastrointestinal health.
More than half of gastrointestinal stromal tumors start in the stomach. Most of the others start in the small intestine, but these types of tumors can start anywhere along the GI tract. A small number start outside the GI tract in nearby areas such as the omentum (an apron-like layer of fatty tissue that hangs over the organs in the abdomen) or the peritoneum (the layer of tissue that lines the organs and walls of the abdomen).
Not all gastrointestinal stromal tumors are cancerous. Some are benign (not cancerous) and don’t grow into other areas or spread to other parts of the body.
Lymphomas are cancers of immune system cells. They rarely begin in the colon or rectum.
Recurrent colorectal cancer is cancer that has disappeared after treatment but has now come back, either in or near the colon or rectum, or in other organs.