Malignant tumor arising from mesenchymal cells that produce cartilage.- Age: usually > 50 years- M > F

Symptoms:- Deep, dull pain (worsens at night, insidious progression over months to years)- Local swelling

Location: Medulla of pelvis and central skeleton

Diagnostics:- X-ray or CT → Osteolysis with moth-eaten appearance→ Calcifications (rings and arcs calcification, popcorn calcification)→ Endosteal scalloping and cortical breach with infiltration of soft tissue- MRI: rim-like contrast enhancement- Biopsy: Lobulated appearance (hyaline cartilage nodules with peripheral calcification )

Treatment:- Surgery (definitive resection) + chemotherapy and radiation therapy