Dedifferentiated chondrosarcoma arising from osteochondromatosis. A case report.

Multiple hereditary osteochondromata has a higher incidence (5%-25%) of malignant change into chondrosarcoma than solitary osteochondroma (1%-2%); but only less than 10% of all chondrosarcomas may undergo dedifferentiated change into fibrosarcoma or malignant fibrous histiocytoma. We have a case presented here with osteochondromatosis who was found to have dedifferentiated chondrosarcoma arising from pelvic osteochondroma. Radical extra-compartmental resection was done and followed by chemotherapy and radiotherapy. Recurrence was found 3 months later. Early recognition of malignant change and adequate surgical resection with adjuvant therapy may prevent local recurrence and increase the survival rate.