Primary pericardial synovial sarcoma: diagnosis of recurrence via multimodal imaging-a case report.

Background: Primary pericardial synovial sarcoma (PSS) is an extremely rare malignancy. Diagnosis and management primarily rely on multimodal imaging, with definitive diagnosis typically requiring a biopsy for histopathological confirmation. Although no established treatment protocol exists, complete tumour resection followed by adjuvant chemotherapy and radiotherapy is often considered. Case summary: A 68-year-old man presented with 1 month of shortness of breath and no significant medical history. Initial examination revealed cardiomegaly, a large pericardial effusion, and a solid mass adjacent to the right atrium. Multimodal imaging, including contrast-enhanced computed tomography and positron emission-T, identified a pericardial mass with metabolic activity. A thoracoscopic biopsy revealed atypical spindle-shaped cells, confirming the diagnosis of synovial sarcoma. This led to total tumour excision and lymph node dissection. Eighteen months post-surgery, imaging revealed recurrence, and the mass from the pericardium near the superior vena cava was resected via thoracotomy. Histopathological examination confirmed recurrent synovial sarcoma. Postoperative chemotherapy was administered; however, lung metastases developed, leading to further treatment 12 months post second surgery. Discussion: PSS is associated with poor prognosis and a high recurrence risk, highlighting the importance of regular follow-up imaging. While complete surgical resection remains the primary treatment, adjunct therapies may improve outcomes. This case underscores the need for multimodal imaging in diagnosing and monitoring PSS.