Key result
SS18 rearrangement identifies rare pulmonary artery synovial sarcoma misdiagnosed as myxoma, with recurrence at 6 months.
Why the study?
Primary pulmonary artery synovial sarcoma is an extremely rare cardiac malignancy often misdiagnosed preoperatively due to nonspecific clinical and imaging features.
Case Report (n=1)
Primary cardiac synovial sarcoma should be suspected over myxoma when multimodal imaging reveals atypical features like a broad base, ill-defined borders, and mild contrast perfusion, with definitive diagnosis requiring molecular testing.
Pulmonary artery masses with atypical features may represent synovial sarcoma with early recurrence; this case leaves open evidence-based diagnostic protocols.
Background: Primary pulmonary artery synovial sarcoma (PPASS) is an extremely rare cardiac malignancy, often misdiagnosed preoperatively due to its nonspecific clinical and imaging features. This case report aims to enhance diagnostic recognition of this rare entity.Case Description: A 35-year-old male presented with chest pain after activity for 1 month. Physical examination revealed stable vital signs and no significant cardiac murmurs. Laboratory tests showed negative immunofixation electrophoresis, unremarkable urinary light chains and coagulation function, and an N-terminal pro-B-type natriuretic peptide (NT-proBNP) level of 2,298 pg/mL. Transthoracic echocardiography (TTE) revealed an irregular solid mass (46 mm × 18 mm) at the pulmonary valve orifice, with a broad base and unclear border. Contrast-enhanced echocardiography showed mild perfusion within the mass. Cardiac magnetic resonance imaging and positron emission tomography/computed tomography (PET/CT) revealed atypical features [ill-defined borders and mild fluorodeoxyglucose (FDG) uptake], raising suspicion for malignancy. The patient underwent surgical resection of the cardiac tumor, pulmonary valvuloplasty, and tricuspid valvuloplasty. Intraoperatively, two distinct tumors were identified and resected. Postoperative pathology revealed a spindle cell tumor. Immunohistochemistry supported a diagnosis of biphasic synovial sarcoma, which was definitively confirmed by fluorescence in situ hybridization (FISH) demonstrating SS18 gene rearrangement. The Ki-67 index was 60%. Six months post-surgery, imaging revealed local recurrence and lung metastases, and the patient received two cycles of ifosfamide, pirarubicin, and mesna chemotherapy with good tolerance.Conclusions: This case highlights the diagnostic challenges of PPASS, which can mimic myxoma on echocardiography. A broad base, unclear border, and atypical contrast perfusion should raise suspicion for malignancy. Definitive diagnosis relies on histopathology and molecular detection of SS18 rearrangement.
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Xiao et al. (2026) conducted a case report in Primary pulmonary artery synovial sarcoma (n=1). Surgical resection was evaluated. A 35-year-old male with a pulmonary artery mass misdiagnosed as myxoma was definitively diagnosed with biphasic synovial sarcoma by SS18 gene rearrangement, developing recurrence at 6 months.
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