Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon.The colon is part of the body’s digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
Gastrointestinal stromal tumors can occur in the colon. See the PDQ summary on for more information. See the PDQ summary about for information about colorectal cancer in children.
Health history can affect the risk of developing colon cancer.Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. Talk with your doctor if you think you may be at risk. Risk factors include the following:
Signs of colon cancer include blood in the stool or a change in bowel habits.These and other signs and symptoms may be caused by colon cancer or by other conditions. Check with your doctor if you have any of the following:
- Stools that are narrower than usual.
- Weight loss for no known reason.
- Feeling very tired.
Tests that examine the colon and rectum are used to detect (find) and diagnose colon cancer.The following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the rectum to feel for lumps or anything else that seems unusual.
- Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps (small areas of bulging tissue), other abnormal areas, or cancer. A sigmoidoscope is inserted through the rectum into the sigmoid colon. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
- Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer.
Certain factors affect prognosis (chance of recovery) and treatment options.The prognosis (chance of recovery) and treatment options depend on the following:
- Whether the cancer has blocked or made a hole in the colon.
- Whether there are any cancer cells left after surgery.
- Whether the cancer has recurred.
- The patient’s general health.