Staging is a way of describing a cancer, such as where it is located, if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancer.
One tool that doctors use to describe the stage is the TNM system. This system uses three criteria to judge the stage of the cancer: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
- For colorectal cancer, “T” describes how deeply the primary tumor has penetrated the bowel lining. (Tumor, T)
- Has the tumor spread to the lymph nodes? (Node, N)
- Has the cancer metastasized to other parts of the body? (Metastasis, M)
Tumor. Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe how deeply the primary tumor has penetrated the bowel lining. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor penetration information is listed below.
TX: The primary tumor cannot be evaluated.
T0: There is no evidence of cancer in the colon or rectum.
Tis: Refers to carcinoma in situ (also called cancer in situ). Cancer cells are found only in the epithelium or lamina propria (the layers lining the inside of the colon or rectum).
T1: The tumor has grown into the submucosa (the layer of tissue underneath the mucosa or lining of the colon).
T2: The tumor has invaded the muscularis propria (a deeper, thick layer of muscle that contracts to force the contents of the intestines along).
T3: The tumor has grown through the muscularis propria and into the subserosa (a thin layer of connective tissue beneath the outer layer of some parts of the large intestine) or into tissues surrounding the colon or rectum.
T4: The tumor has invaded other organs or has caused a perforation (hole) in the wall of the colon or rectum.
Node. The "N" in the TNM system stands for lymph nodes. The lymph nodes are tiny, bean-shaped organs that are located throughout the body that help the body fight infections as part of the body's immune system. There are regional lymph nodes (lymph nodes near the colon and rectum). All others are distant lymph nodes (lymph nodes found in other parts of the body).
NX: The regional lymph nodes cannot be evaluated due to lack of information.
N0: There is no regional lymph node metastasis (the cancer has not spread into the regional lymph nodes).
N1: There is metastatic involvement in one to three regional lymph nodes.
N2: There is metastatic involvement in four or more regional lymph nodes.
Distant metastasis. The "M" in the TNM system describes cancer that has spread to other parts of the body (such as the liver or lungs).
MX: Distant metastasis cannot be evaluated.
M0: The disease has not metastasized.
M1: There is distant metastasis (the cancer has spread to other parts of the body beyond the colon or rectum).
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications.
Stage 0: Refers to cancer in situ. The cancer cells are only in the mucosa (the inner lining) of the colon or rectum. Most colorectal cancers at this stage can be treated by polypectomy (removal of the mass of tissue that develops on the inside wall).
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Stage I: The cancer has grown through the mucosa and has invaded the muscular layer of the colon or rectum. It has not spread into nearby tissue or lymph nodes (T1 or T2, N0, M0).
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Stage IIa: The cancer has spread through the wall of the colon or rectum and may have spread to nearby tissue. It has not spread to the nearby lymph nodes (T3, N0, M0).
Stage IIb: The cancer has spread through the colon or rectum to nearby organs. It has not spread to the nearby lymph nodes (T4, N0, M0).
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Stage IIIa: The cancer has grown through the inner lining or into the muscle layers of the intestine and to one to three lymph nodes, but has not spread to other parts of the body (T1 or T2; N1, M0).
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Stage IIIb: The cancer has grown through the bowel wall or to surrounding organs and into one to three lymph nodes, but has not spread to other parts of the body (T3 or T4, N1, M0).
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Stage IIIc: The cancer (any size) has spread to four or more lymph nodes, but not to other distant parts of the body (any T, N2, M0).
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Stage IV: The cancer has metastasized to distant parts of the body, such as the liver or lungs (any T, any N, M1).
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Recurrent: Recurrent cancer is cancer that has come back after treatment. The disease may be found in the colon, rectum, or in another part of the body.
Tumor grade. Doctors may also use the term "grade," which describes how much the tumor appears like normal tissue. The grade of a cancer can help the doctor predict how quickly the cancer might grow. In cancer that resembles normal tissue, doctors can clearly see different types of cells grouped together (called well differentiated). In a higher-grade cancer, the cancer cells usually look less like normal cells, or "wilder" (called poorly differentiated or undifferentiated). In general, a better-differentiated tumor means a better prognosis.
GX: The tumor grade cannot be identified.
G1: The cells are well differentiated.
G2: The cells are moderately differentiated.
G3: The cells are poorly differentiated.
G4: The cells are undifferentiated.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.cancerstaging.net.
Last Updated: August 10, 2009
