Plain radiographs are the most important investigation for bone tumors. In fact, four of the five common clinical scenarios described in the section Musculoskeletal Tumors - The Five Presenting Complaints require a conventional radiograph as the initial investigation. The only scenario that usually does not require plain radiographs is the patient who presents with a soft tissue mass, although even this condition will require Xrays on some occasions, such as when myositis ossificans is suspected in the list of differential diagnoses.
The plain radiograph is a necessary and cost-effective investigation for patients who present with a bony mass without pain, patients who have incidental radiographic abnormalities, patients with painful bone lesions, and patients with pathologic fractures. The radiographic appearance of the lesion will help the clinician develop an initial differential diagnostic list and determine further clinical and radiographic investigations. For many patients with incidental Xray abnormalities, plain radiographs may be the only test required for follow up.
Analysis of the plain radiographic abnormalities, therefore, is a critical part of the work-up of the musculoskeletal oncology patient. This is made considerably easier if the clinician (or radiologist) asks seven questions while viewing the radiograph. The information gained from this analysis will then be synthesized o allow characterization of the probable biologic potential of the lesion. These seven questions will also facilitate the development of the differential diagnostic lists.
The Seven Questions to Ask in Assessment of Bone Tumor Radiographs
- Where is the lesion? What bone, and in what part of the bone?
- How large is the lesion? How extensive are the abnormalities seen on Xrays?
- What is the lesion doing to the bone?
- What is the bone doing in response?
- Is the lesion making matrix? What kind of matrix is being made?
- Is the cortex eroded?
- Is a soft tissue mass evident?
Once these questions have been answered, in association with the clinical assessment of the patient, the biological activity of the lesion can be classified as benign (latent, active, or aggressive) or malignant. If malignant, the lesion can be classified as probably mesenchymal, myeloproliferative, or metastatic, and if mesenchymal, as high- or low-grade.