The patient went on to have a resection. 

Histology

The tumor is based in the proximal metadiaphysis of the femur but involves metaphysis and diaphysis, with cortical and periosteal breach and soft tissue extension. A athologicalp fracture with tracking haemorrhagee (most prominent medially), contains fragmented tumor.

Sections show a well-differentiated cartilaginous neoplasm based in the medulla, immediately adjacent to a cellular, high grade, poorly differentiated sarcomatous component. The latter dominates the soft tissue extension and grows mainly in an infiltrative, sheet-like pattern. However, some areas form filigree osteoid, raising a differential diagnosis of chondroblastic osteosarcoma.

Dedifferentiated chondrosarcoma is nevertheless favored due to the minimal cytologic atypia in the chondroid component, the abrupt transition, and the predominance of the poorly differentiated portion in the soft tissue extension; some degree of osteosarcomatous differentiation can often be found in association with dedifferentiated chondrosarcoma.

Vascular invasion is identified. 

Final diagnosis: dedifferentiated chondrosarcoma (high grade, grade 3/3).

​​