Dedifferentiated peripheral chondrosarcomas. A report of seven cases.

Peripheral dedifferentiated chondrosarcoma (CS) is an exceedingly rare variant of the highly malignant entity of dedifferentiated chondrosarcoma. Only five such cases have previously been reported. Seven cases are analyzed and evaluated for the presentation and natural history of this highly malignant lesion when it arises in a tumor that was previously an osteochondroma. Both peripheral and central dedifferentiated chondrosarcomas are high-grade malignant lesions and require wide or radical surgical margins for adequate treatment. Despite adequate resection, survival is poor; five of the seven cases presented herein died of metastatic spread of their disease. These cases of the peripheral variant of dedifferentiated chondrosarcoma occurred in patients who were younger than patients with central dedifferentiated chondrosarcomas and may be present with longer duration of symptoms because they occur in previously long-standing benign osteochondromas. As such, they may be easily overlooked clinically and radiographically. Therefore, careful histologic analysis of all cartilage lesions arising on the surface of bone is essential to prevent overlooking foci of high-grade sarcomatous dedifferentiation.