What is colon cancer?

By Philip M. Ginsburg, MD, FACG and Larissa Fopeano, PA-C

Colorectal cancer is a disease in which abnormal cells in the colon or rectum divide uncontrollably, ultimately forming a malignant tumor.

Most colorectal cancers begin as a polyp, a growth in the tissue that lines the inner surface of the colon or rectum. Polyps may grow on the inner surface of the colon or rectum like mushrooms with or without a stalk. Polyps are common in people older than 50 years of age, and most are not cancers. However, a certain type of polyp known as an adenoma may have a higher risk of becoming a cancer.

How common is colon cancer?

Colorectal cancer is the third most common type of non-skin cancer in both men (after prostate cancer and lung cancer) and women (after breast cancer and lung cancer). It is the second leading cause of cancer death in the United States after lung cancer.

Although the major risk factors for colorectal cancer are a family history and older age, several other factors have been associated with increased risk, including excessive alcohol use, obesity, being physically inactive, cigarette smoking, and, possibly, diet.

In addition, people with a history of inflammatory bowel disease (such as ulcerative colitis or Crohn disease) have a higher risk of colorectal cancer than people without such conditions. And people who have a family history of colorectal cancer or certain inherited conditions (such as Lynch syndrome and familial adenomatous polyposis) also have an increased risk of colorectal cancer.

What are the symptoms of colon cancer?

Colorectal cancer usually begins with no symptoms at all. However, over time, there are a number of warning signs that can occur such as:

  • Rectal bleeding
  • Blood in your stool (bright red, black or very dark)
  • A temporary change in your bowel movements, especially in the shape of the stool (e.g., narrow like a pencil)
  • Discomfort in having a bowel movement or the urge to move your bowels without having a bowel movement
  • Frequent cramping pain in your lower abdomen
  • Frequent gas pains
  • Elevated BMI
  • Weight loss without dieting
  • Constant fatigue.

Colon cancer screening

Several screening tests have been developed to help doctors find colorectal cancer early, when it may be more treatable. Some tests that detect adenomas and polyps can actually prevent the development of cancer because these tests allow growths that might otherwise become cancer to be detected and removed. That is, colorectal cancer screening may be a form of cancer prevention, not just early detection.


Colonoscopy every 10 years is the preferred colorectal cancer prevention test. For normal risk individuals, the American College of Gastroenterology recommends colonoscopy every beginning at age 50, and age 45 for African Americans.

Colonoscopy is a procedure which enables a gastroenterologist to directly image and examine the entire colon. It is effective in the diagnosis and/or evaluation of various GI disorders (e.g. colon polyps, colon cancer, diverticulosis, inflammatory bowel disease, bleeding, change in bowel habits, abdominal pain, obstruction and abnormal x-rays or CT scans) as well as in providing therapy (for example, removal of polyps or control of bleeding). It is also used for screening for colon cancer. A key advantage of this technique is that it allows both imaging of abnormal findings and also therapy or removal of these lesions during the same examination.

This procedure is particularly helpful for identification and removal of precancerous polyps.


  1. National Cancer Institute
  2. American Cancer Society. Colorectal Cancer Facts & Figures 2014–2016. Atlanta: American Cancer Society; 2014.
  3. The American College of Gastroenterology.
  4. The American Gastroenterological Association.
  5. www.endoatlas.sk
  6. www.endoatlans.sk