What is colon cancer? Colon cancer is a type of cancer that develops as a result of uncontrolled growth of abnormal cells in the large intestine (colon). The colon, which is an important part of the digestive system, ensures that waste substances are removed from the body. This cancer can develop in any part of the colon, but is most common in the rectum. Colon cancer is usually asymptomatic at an early stage, so [...].