Colon Cancer: The Basics

Author: OncoLink Team
Last Reviewed: January 06, 2023

Colon cancer is caused by colon cells growing out of control. As the number of cells grows, they form into a tumor. Most colon tumors begin when normal colon tissue forms an adenomatous polyp. As the polyp grows larger, a tumor is formed. Colon cancer that has spread from the colon to another part of the body is called metastatic cancer.

Risk Factors

Risk factors include:

  • Personal or family history of colon cancer, polyps, or inherited colon cancer syndromes (such as FAP and HNPCC / Lynch Syndrome).
  • History of ulcerative colitis or Crohn’s disease.
  • Lifestyle factors such as a diet high in fat and red meat and low in fruits and vegetables, high caloric intake, inactivity, and obesity.
  • African American background.


Screening for colon cancer consists of tests that screen for just cancer and tests that screen for both polyps and cancer. Tests that screen for polyps and cancer include:

  • Flexible Sigmoidoscopy.
  • Colonoscopy.
  • Double-contrast barium enema.
  • CT colonography (virtual colonoscopy).

Tests that screen mainly for cancer include:

  • Stool testing for blood.
  • Stool testing for DNA.

Talk to your provider about what age you should start screening and which tests are right for you.

Signs & Symptoms of Colon Cancer

The early stages of colon cancer may not have any symptoms. As a polyp grows into a tumor it can bleed or obstruct the colon, which will then cause symptoms.

  • Bleeding from the rectum.
  • Blood in the stool or toilet after a bowel movement.
  • A change in the shape of the stool, such as thinning.
  • Cramping pain in the abdomen.
  • Feeling the need to have a bowel movement when you don’t actually have to.

Diagnosis of Colon Cancer

After colon cancer is found by a screening test your provider will order tests to determine the extent of the tumor. These tests include:

A pathology report summarizes the results of the biopsy and is sent to your healthcare provider. This report is an important part of planning your treatment. You can request a copy of your report for your records.

Staging Colon Cancer

To guide treatment, colon cancer is "staged." The stage is based on

  • Size and location of the tumor.
  • Whether cancer cells are found in the lymph nodes.
  • Whether cancer cells are found in other areas of the body.

Stage ranges from stage I to stage IV. The stage and type of colon cancer will help guide your treatment plan.


In general, the following treatments are used:

  • Surgery is the most commonly used treatment. During surgery either a polyp and the surrounding tissue are removed or the tumor and surrounding tissues (and lymph nodes if necessary) are removed and the two ends of the remaining colon are reconnected. If it is not possible to reconnect the colon, a colostomy is created.
  • Chemotherapy may be given after surgery to prevent recurrence.
  • Targeted therapy, medications that work specifically against a certain target, can be used to treat certain types of colon cancer.
  • Radiation and interventional radiology procedures can be used to treat areas in the body to which colon cancer spread.

This article is a basic guide to colon cancer. You can learn more about colon cancer and treatment by using the links below.

Colon Cancer: Staging and Treatment

Colorectal Cancer Screening

Colon, Rectal and Anal Cancer: Frequently Asked Questions

Resources for More Information: Colon Cancer

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