Imaging of bone tumors.

In the recent literature on benign bone tumors, papers have highlighted the atypical appearances of intracapsular osteoid osteoma, the characteristic (yet not pathognomonic) feature of fluid-fluid levels on CT and MR imaging of aneurysmal bone cysts, the difficulties of MR imaging of giant cell tumors laden with hemosiderin following intratumoral hemorrhage, and the reliability of ultrasound in measuring the thickness of the cartilage cap in chondroid lesions. MR imaging remains preeminent in the staging of musculoskeletal tumors, although, as yet, there has been only limited success in using this modality for tissue characterization. One study has described certain distinctive patterns on MR associated with different histologies. In particular, peritumoral edema was only found in malignant bone tumors and giant cell tumors. Subjective MR criteria would appear not to be helpful in identifying osteosarcomas patients who are good responders to chemotherapy. Intra-arterial chemotherapy for osteosarcoma of the lower limb may be complicated by infarction of the distal femur, which on MR imaging should not be mistaken for metastatic or transarticular tumor spread.