Dedifferentiated chondrosarcoma.
We reviewed 74 cases of dedifferentiated central and peripheral chondrosarcoma. Histologically these tumours consist of an underlying cartilaginous component (either benign or malignant) juxtaposed to a high-grade non-cartilaginous component, with a typically abrupt transition between the two tissue types. The non-cartilaginous component may constitute a very small or a very large proportion of the tumour, so diagnosis often requires histological evaluation of the entire tumour. The diagnosis is often suspected on the basis of the clinical course and careful evaluation of the radiographic characteristics. Central dedifferentiated chondrosarcoma can be classified radiographically into three types. In type I (36 cases in our review) the radiographic features are the same as those of a central chondrosarcoma, with the addition of a region with very aggressive radiographic features. Type 2 lesions (20 cases) resemble the underlying benign enchondroma but also have destructive changes and/or a large soft tissue mass. Type 3 lesions (8 cases) are not distinctive radiographically and present as a very high grade destructive lesion of bone. These cases are diagnosed following biopsy or tumour resection. The prognosis of these tumours is extremely poor, with 13% overall 5-year survival in this series. Improved survival was found in those cases where diagnosis was prompt and surgical treatment with a wide or radical margin was attained. No benefit was found from the use of adjuvant chemotherapy or radiotherapy. Thus, early recognition of the characteristic radiographic features, adequate histological sampling, and wide or radical surgical margins are necessary for satisfactory management of this highly malignant variant of chondrosarcoma.