Dedifferentiated chondrosarcoma of bone.

Dedifferentiated chondrosarcoma is a highly malignant variant of chondrosarcoma. Approximately 11% of chondrosarcomas can be expected to dedifferentiate into more anaplastic lesions. Radiographic evidence of a benign-appearing cartilage lesion adjacent to a lytic, highly aggressive lesion suggests dedifferentiation. Despite radical surgical treatment, the prognosis is unfavorable, with a 5 year survival rate of 10%.