© 2005-2012 American Society of Clinical Oncology (ASCO). All rights reserved worldwide.
Staging is a way of describing where the cancer is located, if or where it has spread, and whether 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 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 cancers.
One tool that doctors use to describe the stage is the TNM system. This system judges three factors: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to the rest 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:
- How large is the primary tumor, and where is it located? (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 the location of the small bowel tumor. Some stages are also divided into smaller groups that help describe the tumor even in more detail. This helps the doctor develop the best treatment plan for each patient. Specific tumor stage information is listed below.
TX: The primary tumor cannot be evaluated.
T0: There is no evidence of a primary tumor.
Tis: This refers to carcinoma (cancer) in situ. Cancer in situ is very early cancer in which cancer cells are found only in one small area and have not spread.
T1a: There is a tumor in the lamina propria (the innermost layer of the small bowel).
T1b: There is a tumor in the submucosa (the next deepest layer of the small bowel).
T2: The tumor is in the muscularis propria (the third layer of the small bowel).
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 small bowel.
T4: The tumor has invaded other organs or has grown through the lining of the abdominal cavity (the space between the abdomen and the spine that holds several organs) called the visceral peritoneum.
Node. The “N” in the TNM staging system stands for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes near the small bowel are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.
NX: The regional lymph nodes cannot be evaluated.
N0 (N plus zero): There is no regional lymph node metastasis.
N1: Cancer has spread to one to three regional lymph nodes.
N2: Cancer has spread to four or more lymph nodes.
Distant metastasis. The “M” in the TNM system indicates whether the cancer has spread to other parts of the body.
MX: Distant metastasis cannot be evaluated.
M0: The disease has not metastasized.
M1: There is distant metastasis, meaning the cancer has spread to other parts of the body beyond the small bowel.
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications.
Stage 0: This refers to cancer in situ. The cancer is found in only one place and has not spread (Tis, N0, M0).
Stage I: The cancer has grown through the inner layers of the small bowel. It has not spread into nearby tissue or lymph nodes (T1 or T2, N0, M0).
Stage IIA: The cancer has spread through the wall of the small bowel, and it may have spread to nearby tissue. It has not spread to the nearby lymph nodes (T3, N0, M0).
Stage IIB: The cancer has invaded nearby structures outside of the small bowel, but it has not spread to the nearby lymph nodes (T4, N0, M0).
Stage IIIA: The cancer has spread to one to three regional lymph nodes. It may or may not have grown through the inner lining or into the muscle layers of the small bowel, but it has not spread to other parts of the body (any T, N1, M0).
Stage IIIB: The cancer has spread to four or more regional lymph nodes. It may or may not have grown through the inner lining or into the muscle layers of the small bowel, but it has not spread to other parts of the body (any T, N2, M0).
Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs (any T, any N, M1).
Recurrent: Recurrent cancer is cancer that comes back after treatment. The disease may return in the colon, rectum, or another part of the body. If there is a recurrence, the cancer may need to be staged again (called re-staging) using the system above.
In addition to determining the stage of the disease using the TNM system, doctors also determine the histologic grade, which indicates how closely the cancer cells resemble normal tissue under a microscope. In general, the lower the grade, the better the prognosis. A tumor's grade is described using the letter “G” and a number.
GX: The tumor grade cannot be identified.
G1: The cells look more like normal tissue cells (well differentiated).
G2: The cells are somewhat different (moderately differentiated).
G3: The cells look very unlike normal cells (poorly differentiated).
G4: The cells barely resemble normal cells (undifferentiated).
Used with permission of the American Joint Committee on Cancer (AJCC),