Secondary chondrosarcoma.

Secondary chondrosarcoma is a distinctive type of tumor that originates from a preexisting cartilaginous lesion. Most commonly, it is associated with solitary or multiple osteochondromas. A fraction of cases arises from other conditions, such as Maffucci syndrome and Ollier disease. A sudden increase in the size of the cartilaginous cap of an osteochondroma is a sign of malignant transformation to secondary chondrosarcoma. However, there is no strict cutoff in terms of thickness of the cartilaginous cap that can be regarded as being pathognomonic of malignancy. Most cases of secondary chondrosarcoma are low to intermediate grade. Distant metastasis is uncommon, and the prognosis is good for most patients. Overall survival at 5 years is approximately 90%. Surgical resection with wide margins is the best treatment option, but local recurrence remains a significant problem in approximately 10% to 20% of patients. Patients with secondary chondrosarcoma of the pelvis are especially at risk for local recurrence.