[1798] Synovial Sarcoma of the Nervous System: A Clinicopathologic Study of 9 Patients

Julia Keith, Sidney Croul, Leecyn Ang. Sunnybrook Health Sciences Centre, Toronto, Canada; University Health Network, University of Toronto, Toronto, Canada; London Health Sciences Centre, University of Western Ontario, London, Canada

Background: Synovial sarcoma of the nervous system is rare, with only small case series described, and their clinicopathologic features are thus poorly understood.
Design: We reviewed the clinicopathologic features of 9 patients with synovial sarcoma affecting the nervous system. The clinical information and molecular studies were reviewed retrospectively, and a central pathology review was performed including immunohistochemistry for CK (LMW, pan, 7 and 19), EMA, S100, CD34, bcl2, CD99, and Ki67.
Results: The patients were 6 males and 3 males with a median age of 52 years (range 46-74 years). The most common tumour site was spinal nerve (C3-C5, T6, T10 and T12 in 4 cases), followed by the brachial plexus (2 cases), with single cases of the femoral nerve, tibial nerve and sacrum. 8 were primary synovial sarcomas of the nervous system with 1 metastasis from a thoracic primary. 2 cases occurred in patients with previous neurofibroma or Neurofibromatosis Type 1. Most of the lesions were large and enhancing on neuroimaging, were incompletely surgically resected, and recurred after several years (range 1-7 years, average interval to recurrence of 3.4 years). Central pathology review of 12 tumours from 9 patients showed 9 tumours to have a monophasic fascicular growth pattern of oval pleomorphic cells with hemangiopericytomatous vasculature, and myxoid change was present in 4 tumours, prominent in 1. The 3 biphasic synovial sarcomas had a predominantly glandular morphology. The mean mitotic rate was 18 mitoses/10hpf (range of 2-50 mitoses/10 hpf). All tumours had expression of at least 1 of CK (LMW), panCK, or EMA, with panCK being the most commonly expressed antigen (78%). Molecular testing confirmed an SYT/SSX translocation in all cases in which it was performed.
Conclusions: Synovial sarcomas affecting the nervous system are rare, but are usually primary tumours of spinal or peripheral nerves with an aggressive clinical course. Their histology includes monophasic tumours with frequent myxoid change and biphasic predominantly glandular tumours, and they immunolabel with CK or EMA. Recommendations for distinguishing this entity from the major differential diagnosis, MPNST, are made, and the importance of molecular testing is emphasized.
Category: Neuropathology

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 270, Tuesday Afternoon


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