The plain radiograph shows an ill-defined sclerotic lesion with a wide zone of transition involving the proximal tibial epimetaphysis with osteoid matrix and associated irregular periosteal reaction.
The findings are sugggestive of an aggressive lesion and the osteiod matrix characteristic of osteosarcoma.
Osteosarcoma is the most common primary malignant tumor of the bone. It typically occurs in young and adolescent where it is of the primary variety. A second peak occurs in the elderly where it is usually of the secondary variety occuring most often due to malignant degeneration of underlying benign conditions like Paget disease.
Osteosarcomas like any other bone tumor are best diagnosed on plain radiographs which continue to remain the mainstay for diagnosis of bone tumors, followed by histopathology.
CT and MRI, particularly MRI are then performed to locally stage the disease, in which case the study needs to be perfomed with a proper protocol which will include a screening of the whole limb.
The findings that require mention with respect to local staging of the tumor on MRI are:
Presence of transarticular/ transphyseal extension of disease.
Presence of soft tissue component
Encasement of neurovascualr bundles.
Distance of the superior as well as the inferior extent of the lesion from important bony landmarks like greater trochanter in femur and greater tuberosity in humerus.
Presence of skip metastases
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