Tests and diagnosisBy Mayo Clinic staff
Diagnosing colon cancer
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one or more tests and procedures, including:
- Using a scope to examine the inside of your colon. Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view your entire colon and rectum. If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis.
- Using multiple CT images to create a picture of your colon. CT colonography, also called virtual colonoscopy, combines multiple CT scan images to create a detailed picture of the inside of your colon. If you're unable to undergo colonoscopy, your doctor may recommend virtual colonoscopy.
Staging colon cancer
Once you've been diagnosed with colon cancer, your doctor will order tests to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.
Staging tests may include imaging procedures such as abdominal and chest CT scans. In many cases, the stage of your cancer may not be determined until after colon cancer surgery.
The stages of colon cancer are:
- Stage I. Your cancer has grown through the superficial lining (mucosa) of the colon or rectum but hasn't spread beyond the colon wall or rectum.
- Stage II. Your cancer has grown into or through the wall of the colon or rectum but hasn't spread to nearby lymph nodes.
- Stage III. Your cancer has invaded nearby lymph nodes but isn't affecting other parts of your body yet.
- Stage IV. Your cancer has spread to distant sites, such as other organs — for instance to your liver or lung.
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