Abstract
The authors describe the case of a patient with primary monophasic pulmonary synovial sarcoma presenting as a right pleural effusion, and discuss the underlying diagnostic challenges. LEARNING POINTS: There has been tremendous progress in the diagnosis and management of malignant effusion, with thoracoscopic biopsy of the pleura providing the highest diagnostic yield.Even though advanced techniques such as image-guided biopsy and pleuroscopy have relatively high sensitivity and specificity, in rare cases, the diagnosis can still be missed.In clinical practice, all such techniques should be considered in order to achieve an early diagnosis and a better outcome.