Presentation
Pain and swelling of thigh for 4 months.
Patient Data
A well defined lobulated T1 isointense, T2/T2 fat sat heterogeneously hyperintense soft tissue mass lesion adjacent posterior cortex of mid shaft of femur. Involvement of adductor longus, adductor magnus, gracilis and vastus medalis muscles is noted. The lesion has a broad base attached to posterior cortex of femur with cortical thickening. T2 fat sat hyperintense edema surrounding the lesion.
Spiculated periosteal reaction noted radiating perpendicular to the femoral cortex. Osteoid matrix mineralization noted within the mass.
Case Discussion
A diagnosis of periosteal osteosarcoma was made based on the radiological features.
Periosteal osteosarcoma is the 2nd most common juxtacortical osteosarcoma. Common location is the shaft of tibia or femur. Radiological features are of a broad based soft tissue mass attached to the cortex, periosteal reaction perpendicular to the shaft, matrix calcification, cortical thickening/erosions and normal endosteal margin.
The differential diagnosis are:
Parosteal osteosarcoma - densely ossified juxta cortical mass with no perpendicular periosteal reaction.
Juxtacortical chondrosarcoma - dense chondroid mineralization, no perpendicular periosteal reaction.