Malignant Transformation of Synovial Chondromatosis: A Systematic Review

Background: Synovial chondromatosis (SCh) can undergo malignant transformation. Pathologic diagnosis of secondary synovial chondrosarcoma (SChS) is challenging and misdiagnosis may result in over- or undertreatment. Method: A systematic review revealed 48 cases of SChS published in 27 reports since 1957. Data was collected to identify findings indicative of SChS and outcomes of treatment. Results: At median follow-up of 18 months, patients were reported as alive (10%), alive without disease (22%), alive with disease (15%), dead of disease (19%), dead of pulmonary embolism (4%), and unknown (29%). Initial diagnosis of SChS (grade: low/unknown 48%, intermediate/high 52%) was after biopsy in 58%, local resection in 29%, and amputation in 13%. Seventy-four percent of patients underwent 1.8 (mean) resections. Patients treated prior to 1992 were managed with amputation in 79% of cases compared to 48% after 1992. Symptoms were present for 72 mos prior to diagnosis of SChS. Synovial chondrosarcoma demonstrated symptom progression over several months (82%), rapid recurrence after complete resection (30%), and medullary canal invasion (43%). The SChS tumor dimensions were seldom quantified. Conclusion: Malignant degeneration of synovial chondromatosis is rare but can necessitate morbid surgery or result in death. Pathognomonic signs for SChS including intramedullary infiltration are present in the minority of cases. Progression of symptoms, quick local recurrence, and muscle infiltration are more suggestive of SChS. Periarticular cortical erosion, extra-capsular extension, and metaplastic chondroid features are non-specific. Although poorly documented for SChS, tumor size is a strong indicator of malignancy. Biopsy and partial resection are prone to diagnostic error. Surgical decisions are frequently based on size and clinical appearance and may be in conflict with pathologic diagnosis.