Understanding Colon Cancer

"You have cancer." Hearing this will change your life in many ways. One way is that those three small words will expose you to what may sound like a foreign language. If you or your loved one has been diagnosed with colon cancer, the terminology may be confusing.

What is colon cancer?
Colon and rectal cancer (or colorectal cancer) occurs when cells that line the colon grow out of control. It often starts as a non-cancerous growth called a polyp. Certain types of polyps can turn into cancer. This is why polyps found during colon screening are often removed.

Colon cancer usually grows slowly. It can take years for a polyp to get bigger and become cancerous. If not found and removed early enough, colon cancer can spread to other parts of the body.

The stages of colon cancer
When you are first diagnosed, your doctor will determine the stage of the cancer (if - and how far - it has spread). The term "stage" describes how far and where in the body cancer has spread. To determine this, your doctor may do blood or imaging tests. These include CT scan, ultrasound and MRI. You can also expect to have a colonoscopy.

These tests help your doctor determine the stage of cancer. Stages are described in different ways, including Roman numerals and letters.

• Numerical stages go from 0 (the least advanced stage) to IV (the most advanced stage).
• The letters used for describing stages are T (tumor), N (node) and M (metastasis).

T Categories describe how far the tumor has spread into the wall of the colon.

• Tx: There is not enough information to tell how far the tumor has spread into the wall of the colon or rectum.
• Tis: (This is also known as carcinoma in situ or intramucosal carcinoma.) The cancer is only in the inner muscle layer of the colon.
• T1: The cancer has gone through the inner muscle layer of the colon and into the tissue layer below that.
• T2: The cancer has gone through the tissue layer and into the second layer of muscle.
• T3: The cancer has gone all the way through the second layer of muscle and into the outer layer of the colon, but not into any other organs or tissues.
• T4: The cancer has spread into nearby tissues or organs.

N Categories describe whether the cancer has spread to lymph nodes near the primary tumor and, if so, to how many.

• Nx: There is not enough information to be able to tell if the cancer has spread to any lymph nodes.
• N0: The cancer was not found in any lymph nodes.
• N1: The cancer is in one to three lymph nodes near the primary tumor.
• N2: The cancer is in four or more lymph nodes near the primary tumor.

M Categories describe whether the cancer has spread (metastasized) to other parts of the body.

• Mx: There is not enough information to be able to tell if the cancer has spread to other parts of the body.
• M0: The cancer has not been found in any other parts of the body.
• M1: The cancer has spread to other parts of the body.

These categories are grouped together to describe the stage of cancer in detail.

The chart below shows how stages described in Roman numerals and letters correspond.

Stage O Tis, NO, MO	Cancer is present only in the innermost lining of the colon.
Stage I T1, N0, M0 or T2, N0, M0	Cancer has grown into the wall of the colon.
Stage II T3, N0, M0 or T4, N0, M0	Cancer has grown farther into or through the lining of the colon and may have spread to nearby tissue.
Stage III T1-2, N1, M0 or T3, N1, M0or Any T, N2, M0	Cancer has spread to the lymph nodes (types of glands) near where the cancer started.
Stage IV Any T, Any N, M1	Cancer has spread to other parts of the body. Colon cancer often goes first to the liver, but may also spread to the lungs, bones or other parts of the body.

If cancer goes away for a time (called remission), but then comes back, it is called a recurrence. Colon cancer can recur in the colon or in other parts of the body.

Treatment for colon cancer depends on the stage. For early-stage cancers, surgery to remove the cancer may be all that may be needed. For more advanced cancer, you may need to have radiation and chemotherapy.

Related Articles Treating Colon Cancer Colon and Rectal Cancer Myths Abound Will My Cancer Come Back? Coping with the Fear of Recurrence

External Sources American Cancer Society. After diagnosis: staging colon and rectum cancer. Accessed October 11, 2007. American Cancer Society. What is colorectal cancer. Accessed October 9, 2007. Cappell MS. The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps. Medical Clinics of North America. 2005;89:1-42. National Cancer Institute. Colon and rectal cancer. Accessed October 9, 2007. American Cancer Society. How is colorectal cancer staged? Accessed October 9, 2007.

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