Purpose of the study: Secondary chondrosarcoma is rare (1% of malignant bone tumours). Most cases develop from solitary exostosis or concern an exostosis disease. Localisations predominate in the girdles. Management is difficult and no consensus has been reached. The purpose of this study was to present a series of 25 secondary chondrosarcomas in order to improve diagnostic and therapeutic management.

Material and methods: This was a retrospective analysis of 25 cases of secondary chondrosarcoma (10 on solitary exostosis and 15 on exostosis disease) treated by one surgical team from 1970 to 2008. The epidemiological features, clinical signs, radiographic findings, type of treatment and outcome at last follow-up were analysed for the two groups.

Results: Patients with secondary chondrosarcoma were 10 to 20 years young than those with primary chondrosarcoma. There were an equivalent number of men and women and the predominant sites involved flat bones in both groups. The radiographic signs of sarcomatous degeneration most widely observed included heterogeneous calcifications, irregular contours, and soft tissue invasion. Tumours were generally well differentiated. The rate of local recurrence after surgery was 15% at five years and 20% at ten years. Mortality was 2% at five years and 5% at ten years. Most of the deaths occurred after local recurrence. Metastases were identified in four patients after the initial resection. The rate of local recurrence was lower after wide surgical resection.

Discussion: The real objective with secondary chondrosarcoma is to ensure a regular effective follow-up of these patients with a known risk of recurrence (exostosis disease) in order to recognise early signs of sarcomatous degeneration. One of the most reliable signs is recent development of unusual pain on a known exostosis. Education of at-risk patients is crucial and should enable early screening and detection.

Conclusion: Secondary chondrosarcoma occurs 10 to 20 years earlier than primary sarcoma and generally involves the girdles. Outcome and management practices are similar to primary chondrosarcoma. The most important issue is to ensure good patient follow-up in order to enable early diagnosis in patients at risk.