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Staging
Once colorectal cancer is detected, your physician will perform other tests to see whether it has spread. The tumor will be assigned a "stage" depending on the extent of the disease—the further along the stage, the more serious the cancer. In most cases, staging cannot be done until the cancer is removed and analyzed. The size of the tumor alone does not indicate its stage, so pathologists will analyze how deeply into the wall of the colon it extends and whether it has spread elsewhere in the body via the lymphatic vessels and blood vessels.
In some cases, a number of different tests are used to stage colorectal cancer prior to surgery. Some, including X-rays, CAT scans, and magnetic resonance imaging (MRI), are imaging tests to get a better picture of what's going on inside the body. Your doctor may also order laboratory tests to check the components of the blood and to look for carcinoembryonic antigen (CEA), a protein that may signal the presence of cancer.
Staging of colorectal cancer
Stage 0: Tumor is limited to inside of the lining of the colon or rectum.
Stage I: Tumor has invaded several layers of the colon or rectum but has not spread outside the wall.
Stage II: Cancer has grown through the wall of the colon or rectum and invaded nearby tissue, but has not spread to lymph nodes.
Stage III: Cancer has spread to nearby lymph nodes, but not to other parts of the body.
Stage IV: Cancer has spread to other organs and tissues such as the liver, lung, peritoneum, or ovary.
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