Primary orbital synovial sarcoma: A clinicopathologic review with a differential diagnosis and discussion of molecular genetics

Synovial sarcoma is a soft-tissue sarcoma of the extremities developing in young adults that has rarely been reported in the orbit. Synovial sarcoma is associated with a unique translocation, resulting in an SYT-SSX fusion gene. We analyze 7 published periocular cases, together with the current one, to gain a better appreciation of the features of the tumor in this location and to compare the findings with those derived from nonophthalmic studies. An inferior orbital mass developed in a 31-year-old woman after experiencing periorbital and hemifacial pain for more than a decade. Radiographically, the mass was circumscribed and displayed coarse internal calcifications. A large but subtotal excision with histopathologic examination disclosed a primitive tumor composed of spindled and ovoid cells. Immunohistochemistry demonstrated positivity for nuclear transducin-like enhancer of split 1 and membranous CD99, typical for synovial sarcoma. Fluorescence in situ hybridization identified a (X,18) translocation in the tumor cells. The patient underwent postoperative adjuvant proton beam radiotherapy with a good response that has been maintained during 1 year of follow-up. Orbital soft-tissue tumors of all types are increasingly identified by their distinctive genetic signatures that offer more specificity than standard immunohistochemical tests.