Presentation
Right ankle pain
Patient Data
Within the talus, there is a well defined lesion with thin septa and fluid-fluid levels. The lesion has a narrow zone of transition. Minimal reactive marrow edema is seen around the lesion. No cortical destruction, no pathological fracture seen.
Other findings in this case include a partial tear of the anterior talofibular ligament and tibialis posterior tenosynovitis.
Case Discussion
The major differential diagnosis aneurysmal bone cyst (ABC) and telangiectatic osteosarcoma (TO).
One should watch for any hint of aggressiveness. For example, periosteal reaction, cortical breakthrough, or soft tissue mass may suggest TO. However, TO can be entirely lytic and mimic ABC.