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 improve diagnostic capabilities, these tumors 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 dyspnea and was found to have cardiac tamponade. TTE and cardiac MRI revealed a 11.1 cm pericardial mass, which rapidly enlarged to 17.2 cm over three weeks despite partial resection. Pathology confirmed poorly differentiated synovial sarcoma with SS18::SSX2 fusion. Surgical resection and radiation were deemed infeasible due to tumor 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.