Colon, or colorectal, cancer is a malignant growth that arises from the lining of the colon or rectum. Most colon cancers arise slowly from the growth of a benign polyp. The majority of colon cancers occur sporadically. However, colon cancer can also be hereditary and arise from genetic abnormalities, which are transmitted from a parent. The incidence of colon cancer increases with advancing age and most commonly is seen in people over age 50. Men and women are affected equally. Colorectal cancer is the third most commonly diagnosed cancer in the world. It is more common in developed countries.


Symptoms of colorectal cancer depend on the location of the tumor and whether it is confined to the colon or has penetrated through the bowel wall. Right-sided colon cancers typically cause chronic blood loss, which may result in anemia. Left-sided colon cancers may produce frank rectal bleeding or symptoms of bowel obstruction. Early stage colon cancer may cause no symptoms at all. Ideally, these early tumors should be detected by screening before symptoms arise.


Colon cancer is most commonly diagnosed by a colonoscopy. Alternatively, the tumor may be found by performing a barium enema x-ray or an imaging study of the abdomen such as a CT Scan. Once colon cancer is diagnosed, additional testing is indicated to determine if the tumor has penetrated the bowel wall and metastasized to the lymph nodes or other organs such as the liver or lungs.


For people with localized cancer, the optimal treatment is complete surgical removal of the affected section of colon. If the disease has spread beyond the wall of the colon, additional treatment such as chemotherapy or radiation therapy may be necessary.