Fulminant growth of primary pericardial synovial sarcoma despite partial resection: a case report.

Background: Primary pericardial synovial sarcomas are rare and aggressive, with limited data to guide treatment. Though advancements in cardiac imaging have improved diagnostic capabilities, these tumours are often discovered after significant disease progression. We report one of few extremely aggressive cases of pericardial sarcoma that led to in-hospital mortality. Case summary: A 59-year-old woman presented with abdominal pain and dyspnoea and was found to have cardiac tamponade. Transthoracic echocardiogram and cardiac magnetic resonance imaging revealed an 11.1 cm pericardial mass, which rapidly enlarged to 17.2 cm over 3 weeks despite partial resection. Pathology confirmed poorly differentiated synovial sarcoma with SS18::SSX2 fusion. Surgical resection and radiation were deemed infeasible due to tumour size and proximity to critical structures. She received one cycle of anthracycline-ifosfamide chemotherapy but developed airway compromise and died on hospital day 34. Discussion: This case illustrates the rapid progression and poor prognosis of primary pericardial synovial sarcoma, emphasizing that early recognition with multimodality imaging and timely surgical evaluation are crucial, as unresectable disease carries poor outcomes with current systemic therapies.