Primary cardiac synovial sarcoma presenting with right heart failure and superior vena cava syndrome: a multimodal case report.

Introduction: Primary cardiac synovial sarcomas are extremely rare malignant tumors with nonspecific clinical features, often causing delayed diagnosis. Accurate differentiation from other cardiac neoplasms requires immunohistochemistry and confirmation of the SS18-SSX gene fusion via fluorescence in situ hybridization (FISH). Prognosis is poor, with 5-year survival around 35.7%. Multimodal treatment, including surgical resection and adjuvant therapy, is crucial to improve outcomes. Presentation of case: We report the case of a 45-year-old male who presented with a 2-month history of progressive dyspnea, orthopnea, and bilateral lower extremity edema. Imaging revealed a large anterior mediastinal mass compressing the heart, with posterior extension toward the pericardial surface and signs of superior vena cava syndrome. The patient underwent urgent surgical debulking via median sternotomy to relieve compression. No myocardial resection was performed; the tumor was dissected down to the epicardial surface. Histopathological examination confirmed a monophasic synovial sarcoma, and FISH analysis demonstrated the SS18-SSX gene fusion. Adjuvant chemotherapy was administered postoperatively. The patient experienced marked symptomatic improvement and remained clinically stable during follow-up. Discussion: Cardiac synovial sarcomas pose diagnostic and therapeutic challenges due to their rarity and aggressive nature. Surgical excision remains the cornerstone of treatment, although complete resection is often difficult. Molecular diagnostics play a critical role in confirming the diagnosis and guiding management. Adjuvant chemotherapy may contribute to symptom control and disease stabilization, though long-term survival remains limited. This case adds to the limited literature and underscores the importance of early recognition and multidisciplinary intervention. Conclusion: Primary cardiac synovial sarcoma should be considered in the differential diagnosis of cardiac masses presenting with unexplained dyspnea. Early diagnosis, surgical resection, and adjuvant therapy can lead to significant symptomatic relief and may improve survival. This case highlights the value of integrating molecular diagnostics into the routine evaluation of rare cardiac tumors.