Chondrosarcoma. Increasing grade of malignancy in local recurrence.

44 chondrosarcomas were collected during a 22-year period. 40 were classic, 3 mesenchymal, and 1 clear-cell chondrosarcoma. Five (12,5%) were secondary, arising in enchondromatosis, osteochondromatosis and solitary osteochondroma. All the classic chondrosarcomas, initial tumours as well as recurrences, were histologically graded I-III on the basis of cellularity, nuclear size, frequency of lacunae containing multiple nuclei and mitotic rate (Evans). 19 were initially grade I, 14 grade II, and 7 grade III. 18 patients had at least one local recurrence, and 8 of them had 2 or more recurrences. 12 of the 18 patients developed a higher grade of malignancy in the recurrences; only in 6 patients was the grade of malignancy unchanged; 2 of them were initially grade III tumours, however. Because of the high recurrence rate and the risk of increasing malignancy in recurrence, we conclude that the initial treatment should be radical (resection en block, or amputation) even in low grade chondrosarcomas.