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Colon Cancer 101

What is Colon Cancer?

Colon cancer is a disease in which malignant cells form in one or more layers of tissue of the colon. The majority of the time, it begins with the growth of pre-malignant polyps known as adenomas. Over several years, these polyps can grow larger and become malignant, developing into a tumor. Because this process can take time, early detection and screening are important to identify the colon polyps before they develop into cancer. If it is determined that you have colon cancer, it is extremely important to take the time up front to secure a comprehensive diagnosis because the unique biology of your tumor will drive treatment decisions.

Warning Signs of Colon Cancer Development

Men and women, especially those with a personal or family history of colon cancer, polyps, or inherited colon cancer syndromes, should start screening for colon cancer based on their personal presentation, and generally before the age of 50. Also, people with ulcerative colitis or Crohn’s disease are at higher risk and may require screening at an earlier age.

Physical warning signs for colon cancer that should be monitored and may potentially indicate a problem include:

  • Blood in or on the stool
  • Recurrent shifts in normal bowel habits such as experiencing diarrhea or constipation for no known reason
  • Thinning of the stool
  • Increases in stomach discomfort (bloating, gas, fullness and/or cramps that last more than a few days)
  • A feeling that the bowel does not empty completely
  • Weight loss for no known reason
  • Constant and unexplained fatigue

If you are experiencing any of these symptoms, please consult a physician in order to rule out colon cancer or diagnose it early for the best chance at recovery. Please visit the Fight Colorectal Cancer website for more detailed information on warning signs and risk factors.

Detecting Colon Cancer

There are a number of diagnostic tests that a doctor may use to determine whether a patient has developed colon cancer:

  • Sigmoidoscopy, to view the lower third of the colon
  • Colonoscopy, to view the entire colon
  • Physical exam and medical history
  • Family medical history

Stage and Other Factors that Determine Treatment

After cancer has been diagnosed, the stage of the cancer must be established in order to determine the appropriate treatment. The stage is essentially an indicator of how far the tumor has grown into the colon wall, and if it has spread to other parts of the body. To establish the cancer stage, a surgeon removes the tumor and nearby lymph nodes. Lymph nodes are small, ball-shaped organs of the immune system and are found throughout the body, helping to fight infection and disease.

The tumor is examined by a pathologist, who determines how much of the colon wall is involved and if the cancer has grown into the lymph nodes. This information indicates the stage of the cancer. The pathologist will also determine the type of cancer cell and the grade of the tumor, which is determined by how closely the cancer resembles normal colon tissue when viewed under a microscope. Lastly the pathologist will determine whether there has been any vascular invasion by cancer cells and the number of lymph nodes involved. All of this information will be included in your pathology report.

If you are diagnosed with invasive cancer (Stages I, II, III, and IV), your doctor will require a staging workup, including colonoscopy, CEA blood level, chest X-ray, and CT scan of the abdomen and pelvis, to determine if the cancer has spread.

Below is a basic breakdown of how colon cancer is staged:

  • Stage 0 (also called carcinoma in situ) - earliest stage; the cancer is located on the outermost layer of the colon wall.
  • Stage I - the cancer has spread to the second and third layer of the colon wall, but not to the outer colon wall or beyond.
  • Stage II - the cancer has spread through the colon wall without involving lymph nodes.
  • Stage III - the cancer has spread through the colon wall and into lymph nodes, but has not spread to other areas of the body.
  • Stage IV - the cancer has grown from the colon and spread to other areas of the body (i.e. liver and lungs).

Additional tumor testing, such as the Oncotype DX® 1 2 test, can further guide treatment decisions, including whether to undergo chemotherapy following surgery. It is important to take the time to gather all of the information possible about your specific type of colon cancer to guide decisions about your personalized treatment path.

Building a Treatment Plan

Depending on the stage of your colon cancer, your treatment may include removal of polyps, surgery to remove the section of the colon where the tumor is located and lymph nodes, possible chemotherapy, radiation and/or targeted therapies for more advanced cancer. Your physician will recommend a follow-up regimen including exams and tests to watch for recurrence.

No two diagnoses and treatment regimens for colon cancer look exactly the same, which is why learning all you can about your options and talking to your health care team are critical. To empower yourself with personalized information about your type of cancer, please take a few minutes to complete the Colon Cancer Coach questionnaire. You’ll receive a customized report to help you better understand your cancer, and can use the report to discuss next steps with your doctor.

Sources: Fight Colorectal Cancer and The National Cancer Institute


To empower yourself with personalized information about your type of cancer, please take a few minutes to complete the Colon Cancer Coach questionnaire.


  1. Oncotype DX is a registered trademark of Genomic Health, Inc.
  2. At present, the National Comprehensive Cancer Network (NCCN®) has not described the utility of the application of multi-gene assay panels for prognostic or predictive application to colon cancer care. NCCN is a registered trademark of the National Comprehensive Cancer Network. NCCN does not endorse any product or therapy.