Primary mediastinal synovial sarcomas.

Synovial sarcoma is a malignant mesenchymal neoplasm that accounts for approximately 10% of all soft tissue sarcomas. These tumors most commonly occur in the extremities of young adults but are not restricted to this site and can arise in virtually any organ system. Synovial sarcomas originating in the mediastinum are exceptionally rare and are often mistaken for other, more common neoplasms in this location, especially since there are no specific imaging characteristics or clinical manifestations. Contrary to synovial sarcomas of the extremities, mediastinal tumors more commonly affect male patients. Histologically, these tumors can be divided into monophasic, biphasic and poorly differentiated variants, further complicating the diagnostic process. Recent advances in immunohistochemical and molecular techniques have provided useful tools to confirm the diagnosis and distinguish these tumors from other mediastinal neoplasms. The treatment of mediastinal synovial sarcomas often requires multimodal therapy, including surgery, chemotherapy and radiation. Despite this, the prognosis for synovial sarcomas in this location appears to be worse than for their analogues in the soft tissue, likely related to the often large size of the lesions and close proximity to critical anatomic structures making complete surgical resection difficult to achieve. This review summarizes the clinicopathological, immunohistochemical and molecular characteristics of these rare neoplasms.