Primary synovial sarcoma of the mediastinum: a poor prognosis in a 14-year-old girl.

Synovial sarcoma is a soft tissue sarcoma. Its occurrence as a primary mediastinal neoplasm is very rare. We report a case of mediastinal synovial sarcoma in a 14-year-old girl with exertive dyspnoea at presentation. On physical examination, there was a superior vena cava syndrome and café-au-lait spots. Chest X-ray revealed a white left hemithorax with mediastinal deviation to the opposite side. Thoraco-abdomino-pelvic scanner showed a voluminous posterior cervico-mediastinal tissue mass. Computed tomography (CT)-guided biopsy of the mediastino-pleural mass was performed. Histological examination reported fusocellular malignant mesenchymal proliferation. A complementary immunohistological study with a broad range of antibodies was performed with a high-grade single-phase spindle cell synovial sarcoma of the mediastinum. She presented a respiratory distress, did not respond to resuscitation, and died. Mediastinal synovial sarcoma is a rare tumour that is difficult to diagnose. Its slow progression and delay in diagnosis may lead to a fatal evolution.