Synovial chondrosarcoma: a single-institution experience with molecular investigations and review of the literature

Aims: To evaluate the available diagnostic histological criteria for synovial chondrosarcoma and to screen for the presence of IDH1/IDH2 mutations in a series of cases of this malignant cartilaginous neoplasm. Methods and results: Ten cases of synovial chondrosarcoma diagnosed at our institute were reviewed. At presentation, all tumours occurred in adults (median age, 62 years). The most common location was the knee joint (five cases), and the size at diagnosis ranged from 30 mm to 170 mm. Eight patients had secondary synovial chondrosarcomas associated with pre-existing/recurrent or concomitant synovial chondromatosis. Five patients had local recurrences and three had lung metastases. All patients with intralesional excisions developed local recurrences, whereas those who underwent wide resections did not. At last follow-up (mean, 91 months), available for nine patients, seven patients were alive and disease-free, one patient had died of disease, and one was alive with paravertebral metastases. Frequent histological features observed included loss of clustering of chondrocytes (nine cases), the presence of variable amounts of myxoid matrix (eight cases), peripheral hypercellularity (eight cases), tumour necrosis (six cases), and spindling of chondrocytes (four cases). Of the seven cases for which it was possible to evaluate bone permeation, six showed infiltration of bone marrow. All seven cases screened for mutations of exon 4 of IDH1 and IDH2 were found to be wild-type. Conclusions: Histological criteria in correlation with clinical and radiological features allow the recognition of synovial chondrosarcoma. IDH1/IDH2 mutations were not present in synovial chondrosarcoma. Adequate surgical margins are important for disease control