Clear cell chondrosarcoma of bone: long time follow-up of 18 cases.

INTRODUCTION: Clear cell chondrosarcoma is a variant of conventional chondrosarcoma behaving as low grade malignant bone tumor. We reviewed our cases of clear cell chondrosarcoma with the aim to assess the best diagnostic and curative approach to this rare tumor.

MATERIALS AND METHODS: We report 18 cases of clear cell chondrosarcoma treated at the authors' institution. Pertinent clinical information, pre and postoperative serum alkaline phosphatase (SAP) level were obtained from the patients charts. Available imaging studies including plain roentgenograms, computed tomography (CT) images (in 6 patients) and magnetic resonance imaging (MRI) images (in 2 patients).

RESULTS: Eight cases were firstly treated in other institutions, seven with one or more curettage, while one, presented with pathologic fracture, was treated with repeated osteosynthesis. Of the seven patients treated with curettage, five were referred with local recurrence, the mean time between surgical treatment and local recurrence was 52.2 months (from 12 to 132). The other two patients were curetted out 4 and 1 month before, respectively, and were then referred to us to decide about further treatment after incidental diagnosis. Of these cases, three (37.5%) recurred again after our treatment and two of them presented with late bone metastases. Eight patients were originally treated with wide (six) or marginal (two) surgical margins by us. Among them only one proximal humerus (wide margins) had local recurrence 26 months from the first operation. Two patients underwent curettage in our institution, and one of them had a local recurrence. Pre-operative SAP level were obtained in 17 patients. Among them, 11 patients had high pre-operative SAP level (64.7%) and 6 cases were normal. Post-operative SAP levels were obtained in nine patients. After removal of the tumors; SAP levels decreased to normality in seven of the nine patients with high pre-operative SAP. In the other two patients, although the SAP levels were normal, post-operative SAP levels were decreased.

CONCLUSION: Serum alkaline phosphatase can be used as a good tumor marker in diagnosis and follow-up. Due to the occurrence of local recurrences and distant metastasis after curettage, we suggest surgical treatment with "en bloc" resection from the first presentation.