Primary pleural synovial sarcoma (SS) is a rare neoplasm of the pleura. Here we are presenting a case of a middle aged Hispanic male with exudative pleural effusion.
A 51-year-old man presented with progressive worsening shortness of breath for the past 8 months associated with mild dry cough. Pt denied fever or night sweats. PPD was negative. Physical examination revealed decreased breath sounds, dullness to percussion, decreased fremitus and absence of egophony over the right lung. Blood tests showed white cell count of 11,000 (neutrophils 74%), and hemoglobin 11g/dl and platelet count 337,000. A chest X-ray and computed tomography showed a right pleural mild thickening and large effusion. No lung mass was noted. A pleurocentesis showed sanguinous fluid with elevated lactate dehydrogenase and protein suggestive of exudation. A transcutaneous needle biopsy of the pleura was done. Cytologically, smears of specimen revealed malignant spindle cells. Immunohistochemical analysis revealed positive staining of the tumor cells for vimentin and CD99. Rare cells were positive for CAM 5.2, and focal staining for EMA was noted. Both the morphology and staining pattern were suggestive of monophasic pleural SS. Patient improved upon chemotherapy with ifosfamide and Mesna.
Primary pleural SS is rare, and only 16 cases have been reported in the English-language literature (1,2). In a review by Ng et al, 57% of the patients were male, the age ranged from 9 to 69 years, and chest pain followed by dyspnea and cough were the most frequent complaints (1). Radiologically, a mass and / or pleural effusion were noted. Histologically, 50% of the tumors were biphasic with epithelial and spindle cell components. Pleural SS as most SS shows positive staining with cytokeratin, vimentin, EMA, and CD99 (1,2,3,4). Positive bcl-2 staining may be useful in distinguishing SS from malignant mesothelioma (3). The detection of t (X;18)(p11, q11) translocation on cytogenic analysis may be used to confirm the diagnosis of SS (1,2). The translocation results in the fusion of the SYT gene on chromosome 18 to either the SSX1 or SSX2 genes on chromosome X. Most of the monophasic SS has the SYT-SSX2 fusion transcript and has better metastasis-free survival than the biphasic SS which mostly has the SYT-SSX1 fusion transcript. Unlike sarcomatoid malignant mesothelioma, pleural SS is susceptible to chemotherapy and accordingly can be treated (2). Treatment included surgery, chemotherapy and radiotherapy with a prognosis that is similar to that of other SS at other sites of the body(1).
Primay pleural SS should be differentiated from mesothelioma by immunohistochemical staining. It has better response to chemotherapy.
S.G. Khan, None.