Synovial chondrosarcoma of the hip: report of two cases and literature review.

Synovial chondrosarcoma (SCH) is a rare malignant tumour. The lesion may arise de novo in intra-articular space or, more frequently, it may occur as a malignant degeneration of synovial chondromatosis (SC). The authors report two cases of SCH of the hip joint occurring on a SC diagnosed 23 years earlier in one case and 10 years earlier in another case. In both cases the SCH showed an intermediate grade of malignancy at histology (grade 2). In the first case, the patient underwent an external hemipelvectomy and he was disease-free 10 years after the operation. In the second case, the patient refused the proposed amputation and, after palliative radiation therapy, she was alive with disease 58 months after diagnosis. A review of literature reports on SCH was carried out. The knee was the most affected joint, followed by the hip. An amputation was performed in two thirds of cases. Amputation was done as primary surgery in one fifth of cases and for tumour recurrence after synovectomy in four fifth of cases. Metastatic dissemination was seen in 29% of cases. An early detection of malignant transformation of SC might improve the rate of limb salvage surgery in these patients, although no reliable clinical and imaging signs of malignant degeneration have been identified so far.