Bone cancer stages

The staging guidelines developed by the American Joint Committee on Cancer (AJCC) are often used to stage bone cancers, and they allow doctors to communicate important information with each other in a standardized way.

Bone cancer stages are based on four categories:

T (tumor) describes the size of the original tumor.

N (node) indicates whether cancer is present in the lymph nodes.

M (metastasis) refers to whether cancer has spread to other parts of the body.

G (grade) describes the appearance of cancerous tissue and how much it resembles healthy tissue when studied under a microscope.

Bone cancers that contain many different cell types (like healthy tissue does) are considered low grade and generally are slow to grow and spread. Low-grade tumors may also be described as well differentiated.

High-grade bone cancer looks very abnormal compared with healthy tissue and tends to grow and spread more quickly. High-grade tumors may also be described as poorly differentiated.

The bone cancer grade may help your care team determine how quickly the cancer is likely to spread and how best to treat it. The grade influences your prognosis and the likelihood that the cancer will respond well to treatment. Low-grade tumors tend to have a better outlook, while high-grade tumors may be more difficult to treat.

There are four grades designated for bone cancer.

• Grade GX: The grade can’t be determined.
• Grade 1 (G1): Bone cancer closely resembles healthy tissue. This is considered a low-grade tumor.
• Grade 2 (G2): Bone cancer somewhat resembles healthy tissue. This is considered a high-grade tumor.
• Grade 3 (G3): Bone cancer looks very different from healthy tissue. This is considered a high-grade tumor.

After the grade and TNM score are assigned, these measures are combined to determine the cancer’s overall stage.

Stage 1 bone cancer: The cancer cells are still localized to the bone, and the tumor is considered low-grade. Stage 1 bone cancer is divided into two subcategories.

• Stage 1A: The tumor measures about 8 cm or smaller. The grade may be G1 (low grade) or GX (the grade can’t be determined).
• Stage 1B: The cancer is larger than 8 cm or can be found in several places in the same bone. The tumor’s grade may be G1 (low grade) or GX (the grade can’t be determined).

Stage 2 bone cancer: These cancers are still localized to the bone, but they’re considered high grade. Stage 2 bone cancer is divided into two subcategories:

• Stage 2A: The tumor is 8 cm or smaller and high grade ( G2 or G3).
• Stage 2B: The tumor is larger than 8 cm and high grade (G2 or G3).

Stage 3 bone cancer: Primary bone cancers at this stage are still localized to the bone, but they are high grade and have spread to several places within the same bone. These are multiple G2 or G3 high-grade tumors.

Stage 4 bone cancer: This is the most advanced form of the disease. In stage 4, the cancer has spread beyond the bone to other areas of the body. For bone cancer, staging also takes into account how abnormal the cells look under the microscope (the grade). Stage IV bone cancer can be any T or N, meaning the tumor may be any size and may have grown into the lymph nodes. The cancer may be categorized as stage 4A or 4B.

• Stage 4A: The cancer has also spread to the lung(s). The tumor can be any grade.
• Stage 4B: The cancer has spread to the lymph nodes, or the tumor is of any size and grade and has spread to another organ besides the lung. Bone cancer experts typically classify bone cancer stages into localized and metastatic. Stage 4 bone cancer is the same as metastatic cancer. The tumor can be any grade.

Recurrent bone cancer

Bone cancer may return after treatment concludes, which is called recurrent bone cancer. After treatment, people with bone cancer may receive follow-up care to check for any signs of recurrence.

With recurrent bone cancer, further testing is done to restage the cancer and determine where and how much it’s spread. The tests used to restage recurrent bone cancer usually resemble the tests used to diagnose and stage the original cancer.

Learn more about orthopedic oncology

Next topic: How is bone cancer diagnosed?