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| Staging of Musculoskeletal Sarcomas |
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| Written by Sean V. McGarry, MD |
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Introduction Tumor staging uses parameters such as histologic grade, anatomic location and size, and presence or absence of nodal or metastatic disease, to help categorize tumors. Once a stage is determined, it can help health care providers determine a patient’s prognosis, as well as a treatment plan. Physicians use two classification systems in the staging of musculoskeletal sarcomas. The Enneking classification system (also known as the Surgical Staging System of the Musculoskeletal Tumor Society) uses the same criteria for bone and soft tissue sarcomas and gives a diagnosis of grade I, II or III. The American Joint Committee on Cancer (AJCC) system uses one set of criteria for bone sarcomas and another for soft-tissue sarcomas and gives a diagnosis of grade I, II, III or IV. The Enneking system is used almost exclusively by orthopaedic oncologists and is the language used in orthopaedic institutions. Use of the AJCC system is more widespread and allows communication between specialties such as surgical oncology, medical oncology, and radiation oncology. The goal of the AJCC is to provide a common language to be used in classifying cancer and directing treatment. Musculoskeletal sarcomas rarely metastasize via the lymph system. Hence, the Enneking classification system does not include nodal disease in the staging process. Nodal disease in the AJCC system confers a stage IV diagnosis. AJCC Staging System for Soft-Tissue Sarcoma The four parameters used in the AJCC Staging System for Soft-Tissue Sarcoma are grade, tumor size and location, nodal disease and metastatic disease. The following provides an overview of these parameters: Grade (G) G1 Well differentiated G2 Moderately differentiated G3 Poorly differentiated G4 Undifferentiated Tumor Size and Location T1 Small size (≤ 5 cm) T1a superficial to fascia T1b deep to fascia T2 Large size (>5 cm) T2a superficial to fascia T2b deep to fascia Nodal disease N0 No nodal disease N1 Nodal disease present Metastatic disease M0 No metastatic disease M1 Metastatic disease present Again note that sarcoma rarely metastasizes via the lymphatic system. When they do, it confers stage IV disease regardless of any of the other parameters. If there is nodal disease without any other evidence of metastases then it is grade IVA. Once a stage has been determined then treatment guidelines such as those offered by the NCCN (National Comprehensive Cancer Network) or ASCO (American Society of Clinical Oncologists) can be used to direct therapy. By starting with a common system for staging treatment different therapies and their results can be compared.  AJCC Staging System for Bone Sarcoma The AJCC Staging System for Bone Sarcoma uses four parameters: grade, tumor size and location, nodal disease and metastatic disease. Grade (G) G1 Well differentiated G2 Moderately differentiated G3 Poorly differentiated G4 Undifferentiated Tumor Size and Location T1 Small size (≤ 8 cm) T2 Large size (>8 cm) T3 Discontinuous tumor within the same bone (skip metastasis) Nodal disease N0 No nodal disease N1 Nodal disease present Metastatic disease M0 No metastatic disease M1 Metastatic disease present M1a pulmonary metastasis M1b metastases other than pulmonary Again note that sarcomas rarely metastasize via the lymphatic system. When they do, it confers stage IV disease regardless of any of the other parameters. If there is nodal disease without any other evidence of metastases then it is grade IVA. As an example, a patient presents with a high-grade osteosarcoma involving the distal third of the femur (12 cm in greatest dimension). A CT scan of the chest shows no evidence of pulmonary disease. There is no known nodal disease. Grade this is G3-4. Tumor size is T2. Nodal disease is N0. Metastastic disease is M0. This patient has stage IIB disease.  Enneking Staging System The Enneking Staging System for Sarcoma (for bone and soft tissue) uses three parameters: grade, tumor size and location, and metastatic disease. This is the language that is used in orthopaedic circles to describe musculoskeletal sarcomas. It is not used outside of orthopaedics and would not be familiar to most medical oncologists or radiation oncologists. Grade (G) G1 Low grade G2 High grade Tumor Size and Location T1 Intra-compartmental T2 Extra-compartmental In bone sarcomas, the involved bone is considered a compartment. Therefore, a bone sarcoma with soft-tissue extent is extra-compartmental. Metastatic disease M0 No metastatic disease M1 Metastatic disease present  References
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