1. Primary thoracic sarcomas are extremely rare and include chondrosarcoma, synovial sarcoma, and fibrosarcoma. These tumors usually manifest as endoluminal tracheal masses.

2. Conclusions: Dedifferentiated chondrosarcoma arising in a preexisting osteochondroma is an extremely rare lesion with a poor prognosis.

3. Intracranial mesenchymal chondrosarcoma is one of the rare tumors of the central nervous system, which often presents as an aggressive-appearing extra-axial hypervascular tumor at the falx cerebri.

4. This pelvic CT scan demonstrates a chondrosarcoma involving the right pelvic wing.

5. Myxoid Chondrosarcoma is a rare, soft tissue tumor a characteristic histologic appearance.

6. We report a case of primary intraspinal mesenchymal chondrosarcoma in an 11 - year - old boy.

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7. The differential diagnosis among chondrosarcoma, chordoma, and chondroid chordoma is important due to their different prognoses.

8. Chondrosarcoma of the mandible is uncommon, It is a malignant tumor of cartilagionous origin.

9. Dedifferentiated chondrosarcoma(DDCS)comprises approximately 10%of all chondrosarcomas and has the worst outcome with a 5-year survival of 10%.

10. We also review the other subtypes of chondrosarcoma and discuss the differential diagnosis of an aggressive-appearing extra-axial hypervascular tumor at the falx cerebri.

11. Chondrosarcoma of the mandible is uncommon, It is a malignant tumor of cartilaginous origin.

12. Conclusion. Wide or marginal en bloc excision of sacral chordoma and chondrosarcoma is associated with significant improvement in disease-free survival with acceptable perioperative morbidity rate.

13. Chordoma is a more common tumor in this location than chondrosarcoma.

14. Microscopic examination and immunohistochemical studies confirmed the diagnosis of mesenchymal chondrosarcoma.

15. Among them, there were 7 osteosarcomas, 5 giant cell tumors, 1 malignant fibrous histiocytoma, 1 chondrosarcoma and 1 osteoblastoma.