Primary Pleural Synovial Sarcoma : A Rare and Agressive Presentation in a 53 – Year - Old Female Patient

Synovial sarcoma is a rare mesenchymal tumor, usually found in the extremities. Its primary occurrence in the pleura is exceptional and presents a major diagnostic and therapeutic challenge. We report the case of a 53-year-old female patient presenting with progressive chest pain and dyspnea. Radiological imaging (chest X-ray and CT scan) revealed multiple large pleural masses with bilateral nodules. Pleural biopsy showed a spindle cell proliferation with mesenchymal features. Immunohistochemical analysis revealed strong expression of TLE1, while cytokeratins AE1/AE3, SATB2, S100, and desmin were negative. This immunophenotypic profile, combined with the morphological features, supported the diagnosis of pleural synovial sarcoma. In the absence of genetic confirmation of the t (X ;18) (p11 ; q11) translocation, the diagnosis relied on strong histopathological and immunohistochemical suspicion. Chemotherapy with anthracyclines was planned, but the patient unfortunately died before treatment initiation. Pleural synovial sarcoma is an extremely rare entity whose diagnosis depends on morphological, immunohistochemical, and ideally molecular findings. Its clinical presentation is often nonspecific, and its course can be rapidly unfavorable. TLE1 expression is a sensitive marker but not specific, highlighting the importance of a multidisciplinary diagnostic approach. This case underlines the necessity of considering synovial sarcoma in the differential diagnosis of unusual pleural masses, especially in younger patients. Rapid management is essential, although the prognosis remains poor in aggressive forms.