ON THIS PAGE: You will learn about how doctors describe a cancer’s growth or spread, as well as the way the tumor cells look when viewed under a microscope. This is called the stage and grade. Use the menu to see other pages.
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What is cancer staging?
Staging is a way of describing where the cancer is located, if and where it has spread, and whether it is affecting other parts of the body.
Doctors use diagnostic tests to find out the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor recommend the best kind of treatment, and it can help predict a patient's prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancer.
In general, bone sarcomas are described as:
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Localized. A sarcoma that is able to be surgically removed.
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Locally advanced. A sarcoma that has not spread to other body parts but cannot be easily surgically removed.
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Metastatic. A sarcoma that has spread to other body parts, such as the lungs or other bones.
TNM staging system
While not commonly used to make treatment decisions for bone sarcomas, one tool that doctors use to describe the stage is the TNM system. Doctors use the results from diagnostic tests and scans to answer these questions:
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Tumor (T): How large is the primary tumor? Where is it located?
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Node (N): Has the tumor spread to the lymph nodes? If so, where and how many?
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Metastasis (M): Has the cancer spread to other parts of the body? If so, where and how much?
The results are combined to determine the stage of cancer for each person.
In most primary bone sarcomas, there are 4 stages: stages I through IV (1 through 4).
Here are more details on each part of the TNM system for bone sarcoma:
Tumor (T)
Using the TNM system, the “T” plus a letter or number (0 to 4) is used to describe the size and extent of the tumor, and it differs depending on where the bone sarcoma is located. Tumor size is measured in centimeters (cm).
Node (N)
The “N” in the TNM staging system stands for lymph nodes. These small, bean-shaped organs help fight infection. Lymph nodes near where the cancer started are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes. Bone sarcomas rarely spread to lymph nodes, so removing them is not generally needed.
NX: The regional lymph nodes cannot be evaluated.
N0 (N zero): The cancer has not spread to the regional lymph nodes.
N1: The cancer has spread to the regional lymph nodes. This is rare for primary bone sarcoma.
Metastasis (M)
The “M” in the TNM system describes whether the cancer has spread to other parts of the body, called metastasis.
M0 (M zero): The cancer has not metastasized.
M1: The cancer has metastasized to another part of the body.
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M1a: The cancer has metastasized to a lung.
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M1b: The cancer has metastasized to other bones or another organ.
Grade (G)
Doctors also describe primary bone sarcoma by its grade (G). The grade describes how much cancer cells look like healthy cells when viewed under a microscope.
The doctor compares the cancerous tissue with healthy tissue. Healthy tissue usually contains many different types of cells grouped together. If the cancer looks similar to healthy tissue and has different cell groupings, it is called "well differentiated" or a "low-grade tumor." If the cancerous tissue looks very different from healthy tissue, it is called "poorly differentiated" or a "high-grade tumor." The cancer’s grade may help the doctor predict how quickly the cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.
GX: The tumor grade cannot be identified.
G1: The cancer cells are well differentiated (low grade).
G2: The cancer cells are moderately differentiated (high grade).
G3: The cancer cells are poorly differentiated (high grade).
Stage groups for bone sarcoma
Doctors assign the stage of the cancer by combining the T, N, M, and G classifications (see above). There are no stage groupings for primary bone sarcoma in the spine or pelvis. These stage groupings are only for skeleton, trunk, skull, and facial bones:
Stage IA: The tumor is low grade or cannot be graded (G1 or GX) and 8 cm or smaller (T1). It has not spread to any lymph nodes or to other parts of the body (N0, M0).
Stage IB: The tumor is low grade or cannot be graded (G1 or GX) and larger than 8 cm (T2) or there are more than 1 separate tumors in the primary bone site (T3). It has not spread to any lymph nodes or to other parts of the body (N0, M0).
Stage IIA: The tumor is high grade (G2 or G3) and 8 cm or smaller (T1). It has not spread to any lymph nodes or to other parts of the body (N0, M0).
Stage IIB: The tumor is high grade (G2 or G3) and larger than 8 cm (T2). It has not spread to any lymph nodes or to other parts of the body (N0, M0).
Stage III: There are multiple high-grade (G2 or G3) tumors in the primary bone site (T3), but they have not spread to any lymph nodes or to other parts of the body (N0, M0).
Stage IVA: The tumor is of any size or grade and has spread to the lung(s) (any G, any T, N0, M1a).
Stage IVB: The tumor is of any size or grade and has spread to the lymph nodes (any G, any T, N1, and any M), or the tumor is of any size or grade and has spread to another bone or organ besides the lung (any G, any T, any N, M1b).
Recurrent: Recurrent cancer is cancer that has come back after treatment. If the cancer does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.
In general, patients with the best prognosis have:
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A T1 or T2 tumor
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A low-grade tumor (G1)
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A tumor that is easily removed with surgery, such as those located in an arm or leg
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A localized tumor that has not spread
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Certain genetic changes
Used with permission of the American College of Surgeons, Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017), published by Springer International Publishing.
Information about the cancer’s stage and grade will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.