Clear-cell chondrosarcoma with elevated alkaline phosphatase, mistaken for osteosarcoma on biopsy

This paper report a case of a pelvic clear-cell chondrosarcoma that was initially diagnosed as clear-cell osteosarcoma after needle biopsy. Preoperatively, laboratory studies revealed an elevated alkaline phosphatase and needle biopsy showed clear cells producing osteoid. Internal hemipelvectomy was performed and final pathology was most consistent with clear-cell chondrosarcoma, despite a negative S-100 immunohistochemical stain. Distinguishing between these two entities is clinically important because treatment differs. In this case, the patient did not receive pre-or postoperative chemotherapy and is disease free more than 2 years later.