Rare Occurrence of Synovial Sarcoma Originating from Dura Mater

Synovial sarcomas are not derived from synovium; they originate from primitive mesenchymal stem cells and can be seen in regions without synovium. [] Synovial sarcomas are mostly seen on extremities; however, they may be distributed widely across the head and neck, mediastinum, abdomen, lung, pleura, kidney, and gastrointestinal tract.[] These tumors have been reported to exist intracranially in the dura mater and base of the skull, indicating that they may be present anywhere in the body.[]

Clinical presentation of meningothelial mesenchymal tumors includes their anatomic location and diameter. The affected patients mostly present with nausea, vomiting, headache, paresthesia, memory impairment, convulsions, disequilibrium, aphasia, and hearing loss. Neuroradiological examination has reportedly revealed meningeal-originated tumor and a range of dissemination.[]

The appearance of these tumors is related to differentiation and resembles extracranial soft tissue sarcomas. Rapidly progressive tumors are poorly demarcated, fragile, hemorrhagic, necrotic, and cystic. [] Histologically, synovial sarcomas are differentiated into four subtypes: monophasic, monophasic epithelial, biphasic, and poorly differentiated types. [,] The present case was classified as poorly differentiated synovial sarcoma because cystic, solid component and intratumoral hematoma were observed.

Based on the location and morphological features, the tumor in the present case was histopathologically different from meningioma, solitary fibrous tumor, and others sarcomas.[] In addition to 100% immunoreactivity for EMA, 86%-90% nuclear positivity PgR is observed in meningiomas.[,] In the present case, contrary to EMA positivity, PgR was negative. Solitary fibrous tumors may also be located in central nervous system. They are negative for cytokeratin and EMA, while diffuse positivity is observed with CD34.[] Although the present case was positive for CD34 and negative for cytokeratin, positive immunoreaction for EMA was inconsistent with the solitary fibrous tumor. Approximately 10%-20% of synovial sarcomas have the same pattern as hemangiopericytomas.[] Like peripheral nerve sheath tumors, 30% of monophasic and poorly differentiated synovial sarcomas show nuclear and cytoplasmic S- 100-positive immunoreaction.[] The immune reaction to EMA and cytokeratin is negative in malign peripheral nerve sheath tumors; thus, these tests may be used in differential diagnosis.[] In the present case, similar to malign peripheral nerve sheath tumors, S-100 was immunoreactive, but unlikely EMA was immunoreactive either. Recently, high expression of TLE-1 has been observed in synovial sarcomas. In the present case, TLE immunoreactivity was positive; this feature is specific and sensitive for synovial sarcomas.[] Furthermore, in this case, Ki-67 proliferation index was 12%. However, because synovial sarcoma-specific chromosomal translocation (X; 18) (p11; q11) was seen, diagnosis was made based on the findings of histological and immunohistochemical tests in the present case.[ Dura mater and leptomeningeal synovial sarcomas are very rarely seen, so optimal systematic treatment has not been established.[] Wide surgical resection, radiotherapy, and doxorubicin-based chemotherapy may prevent local recurrence of the tumor and improve prognosis.[,,]