Authors: Hartel Paul H, Parker John E
Pulmonary synovial sarcoma is a rare tumor with characteristic SS18/SSX translocation. Fusion products comprising this translocation are predominantly types 1 or 2 with only rare cases of fusion types 3 or 4. We evaluated eight cases of primary synovial sarcoma with SS18/SSX fusion type 4 to better define this rarely studied cohort of patients. We found patients with tumours showing SS18/SSX fusion type 4 are younger than those with fusion type 1 or 2 and showed cases of overall survival of nearly 10 years. Radiologically, in contrast to soft tissue synovial sarcoma, calcification, high vascularity, bone or chest wall invasion was not seen. Histology unusual in pulmonary synovial sarcoma was found in 63% of fusion type 4 cases compared with 21% in reported cases of fusion type 1 and 2. Although fusion type 4 is a rare finding in an already rare tumour, and while additional cases are needed, SS18/SSX fusion type 4 may impart unique clinical and histologic characteristics.
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