Chondrosarcoma arising in osteochondroma.

Secondary chondrosarcomas are rare. An analysis of 75 cases of chondrosarcomas secondary to osteochondroma (42 lesions were from the Mayo Clinic files and 33 were from consultation files) revealed that 40 of the patients had single exostosis and 35 had multiple lesions. More males than females were affected, and most of the patients were age 20 to 40 years. The tumors involved various bones. Malignant change was manifested radiologically by fuzzy margins of the cartilage cap and by the presence of lucent zones within the lesion. Grossly, the surface of the thickened cartilage cap is irregular. Microscopically, most of the tumors were well-differentiated (Grade 1). Treatment was surgical. Simple excision of the tumor resulted in a large recurrence rate. Resection and amputation were generally curative. Only 12 of the patients have died of their tumor. Most patients died of local recurrence. Only two of the 75 patients had definite evidence of metastatic disease.