A low-grade chondrosarcoma may develop an area of high-grade sarcoma. This is termed "dedifferentiation". It may be associated with a worse prognosis for the patient.
Synonym: chondrosarcoma with additional mesenchymal component
Dedifferentiation may affect a chondrosarcoma of bone or an extraskeletal chondrosarcoma.
Types of high grade sarcoma that may develop:
(1) malignant fibrous histiocytoma
(2) osteosarcoma
(3) leiomyosarcoma
(4) spindle cell sarcoma
(5) pleomorphic rhabdomyosarcoma
(6) fibrosarcoma
(7) angiosarcoma
Areas of dedifferentiation may be identified on MRI scans as areas of lower signal intensity lacking lobulation.
Risk factors for a poor outcome:
(1) metastases from the high-grade sarcoma
(2) dedifferentiated component constituting a high percent of the tumor
(3) malignant fibrous histiocytoma
(4) incomplete resection
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