"Tumoral" enthesopathy: a juxtacortical osteosarcoma simulation.

A patient with psoriatic arthritis involving the ankles and feet developed a rapidly progressive large juxtacortical bony proliferative lesion arising from the right proximal radius at the bicipital tendon insertion site. The radiographic pattern was compatible with a juxtacortical periosteal osteosarcoma. We discuss the similar radiographic findings between a surface osteosarcoma and florid inflammatory enthesopathy that was found upon biopsy.