Are the features of a quiescent or aggressive lesion?
Aggressive. The cortical erosion with wide zone of transition is the most important finding to assess biological behaviour. A benign, slow growing mass may remodel the adjacent bone but result in a smooth and sharply demarcated border.
Rounded but ill-defined soft tissue swelling is located posteromedial to the femur. There is evidence of cortical erosion which appears to have a relatively wide zone of transition. The mass itself demonstrates no calcification. Incidental note is made of contrast in the bladder from preceding CT scan (not shown).