Presentation
Large painful swelling over the left lower thigh and around knee joint.
Patient Data
Radiograph distal thigh including knee joint shows large fluffy chondroid matrix mass centered around distal femoral shaft.
Also noted is linear multi-layered periosteal reaction in femoral shaft.
Lesion is extending upto articular surface of knee joint and with probable intra-articular extension.
Case Discussion
Due to typical fluffy ring and arc like chondroid matrix probable diagnosis of chondrosarcoma was given.
On histopathology it turned out to be "osteogenic sarcoma with secondary chondroid degeneration".
Chondroblastic osteosarcoma, although very rare, is a differential that must always be considered in relation to chondrosarcoma, particularly in a young population and in long bones as in this case.