Dedifferentiated clear cell chondrosarcoma

Dedifferentiation, a change in the histologic character acid clinical behav ior of a tumor to a more immature and aggressive one, occurs in approximate ly 11% of all chondrosarcomas. The original lesion is usually a low-grade c hondrosarcoma. Clear cell chondrosarcoma is a rare cartilaginous tumor of l ow-grade malignancy with a preference for the ends of long bones. It is usu ally curable by resection. Recurrence commonly follows inadequate surgery, and metastases to lung, brain, and bones can develop. However, dedifferenti ation has not yet been described in association with clear cell chondrosarc oma. Three patients are described who were initially diagnosed as having cl ear cell chondrosarcoma of the femur. Two were treated with en bloc resecti on fur a clear cell chondrosarcoma. One of these had an undifferentiated sa rcoma in a local recurrence after 6 years. In the second, metastasis of the clear cell chondrosarcoma developed 51/2 years after surgery; autopsy reve aled undifferentiated sarcoma in the lung, heart, and lumbar spine. The thi rd patient had dedifferentiated clear cell chondrosarcoma at the time of re section following the biopsy diagnosis of clear cell chondrosarcoma. All th ree died with metastatic disease. These three patients represent three diff erent manifestations of dedifferentiation-at initial diagnosis, at: recurre nce, and at metastasis. To our knowledge, this is the first description of dedifferentiation ion occurring in clear cell chondrosarcoma.