Staging studies may be needed to determine the local extent of lesions or distant metastases and histologic diagnosis of the disease.

Radionuclide bone scans are performed to assess multiple sites of involvement, the extent of local intraosseous involvement not apparent on radiographs, and tumor activity.

Computed tomography (CT) of the lesion is employed for determining bone destruction, intrinsic density of the lesion, and cortical extension. Metastases of primary musculoskeletal sarcomas are most commonly found in the lungs. Chest radiographs and chest CT are used for chest surveillance to provide information about metastatic disease. The role of combined positron emission tomography and computed tomography (PET/CT) is unclear, but it has been most useful in delineation of neurofibromas from sarcomas in patients with neurofibromatosis.

Magnetic resonance imaging (MRI) delineates the precise location and extent of tumor involvement. Specifically, MRI is the primary study used to delineate compartmental involvement, intraarticular involvement, and proximity of neurovascular structures; MRI provides superior resolution and sensitivity in depicting abnormalities and is particularly useful in determining the extent of soft tissue lesions and the subtle involvement of the bone marrow in bone lesions.

Staging. The staging system for musculoskeletal tumors shown in Table 6-1 represents an assessment of the surgical grade, local extent of disease, and presence or absence of metastases. It is based on the stratification and interrelationship of these three factors and is used to predict the prognosis, response to surgical treatment, risk of local recurrence, and metastatic potential.