This 12-years old boy presented with pain in the leg after playing football. The plain radiograph shows an expansile, osteolytic lesion with a sclerotic rim, suggesting that it is benign. It is likely cortical, but this is difficult to be sure about. There seems to be a pathologic fracture, the reason why the boy is now symptomatic.
An MRI was done. It shows a STIR dark lesion with marrow edema, consistent with a fibro-osseous lesion with a pathologic fracture. The CT scan done prior to the biopsy shows the pathologic fracture well with some bone fragment along the posterior endosteal margin.
The likelihood was of an osteofibrous dysplasia given the location.
A biopsy was done. The final diagnosis was non-ossifying fibroma.