The staging guidelines developed by the American Joint Committee on Cancer (AJCC) are often used to stage bone cancers and allow doctors to communicate important information about the cancer with each other in a standardized way. Bone cancer stages are based on four categories:
T (tumor): This describes the size of the original tumor.
N (node): This indicates whether the cancer is present in the lymph nodes.
M (metastasis): This refers to whether cancer has spread to other parts of the body.
After the TNM score is assigned, bone cancer will be classified into one of the stages below:
Stage I (stage 1 bone cancer): The cancer cells are still localized to the bone, and the tumor is considered low-grade. Stage I bone cancer is divided into two subcategories:
Stage II (stage 2 bone cancer): These cancers are still localized to the bone, but they are considered high-grade. Stage II bone cancer is divided into two subcategories:
Stage III (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.
Stage IV (stage 4 bone cancer): Stage IV bone cancer is the most advanced form of the disease. In stage IV, 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 Tor N, meaning the tumor may be any size and may have grown into the lymph nodes. The cancer may be categorized as stage IVA or IVB: