Key result
Repeated targeted biopsy and multimodal imaging overcome false negatives to diagnose primary pericardial synovial sarcoma.
Why the study?
Primary pericardial synovial sarcoma is exceptionally rare with poor survival, and diagnosis is often delayed because initial biopsies can be nondiagnostic and distinguishing malignancy from inflammatory disease is challenging.
Case Report (n=1)
This case highlights the diagnostic challenges of primary pericardial synovial sarcoma, emphasizing the need for repeated targeted biopsies and multimodality imaging when initial results are nondiagnostic.
Supports considering repeat targeted biopsy after nondiagnostic results in pericardial masses; leaves open optimal diagnostic algorithms for rare sarcomas.
Background Primary malignant pericardial tumors are extremely rare and synovial sarcoma arising from the pericardium is an exceptionally uncommon entity with poor survival. Diagnosis is often delayed because initial pericardial biopsies can be nondiagnostic, and distinguishing between inflammatory disease and malignancy may be challenging. Case summary An 11-year-old boy developed recurrent fever and chest pain 15 days after COVID-19 infection. Echocardiography demonstrated pericardial effusion, and pericarditis was suspected. Despite drainage of hemorrhagic effusion, pericardial biopsy showed only fibrous thickening. Two months later, recurrent effusion and hematoma enlargement prompted repeat evaluation, but multimodal imaging including CT, MRI, and catheterization failed to identify the etiology. At three months, worsening hematoma around the left ventricular posterior wall necessitated surgical excision. The mass was tightly adherent to the pericardium, precluding complete resection. Histology revealed spindle-shaped tumor cells, and molecular testing confirmed SS18::SSX fusion, leading to a diagnosis of synovial sarcoma. 18F-FDG PET/CT showed pericardial uptake without distant disease. The patient underwent chemotherapy, radiotherapy, and high-dose chemotherapy with autologous stem cell rescue. He remained in remission for 18 months, but subsequently developed brain metastases and died. Discussion This case highlights the diagnostic difficulty of primary pericardial synovial sarcoma. Initial biopsy may be falsely negative, and repeated sampling directly from the lesion is crucial when a cardiac tumor is suspected. Furthermore, 18F-FDG PET/CT proved valuable not only for diagnostic assessment but also for therapeutic monitoring. In summary, repeated targeted biopsy and multimodality imaging are essential for accurate diagnosis and management of this rare cardiac malignancy.
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Mori et al. (2026) conducted a case report in Primary synovial sarcoma of the pericardium (n=1). Repeated targeted biopsy and multimodality imaging was evaluated. Repeated targeted biopsy and multimodality imaging were essential to diagnose primary pericardial synovial sarcoma in an 11-year-old boy presenting with recurrent hemorrhagic effusion.
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