Case Report and Diagnostic Implications of Misdiagnosis of Pericardial Myxoid Liposarcoma by Multimodal Imaging

Juan WangXijun ZhuQian Liu^*Dong Wang^*Li-Xia SunYu-Ling SongLai WuYun-Long Cao

• Binzhou Medical University Hospital, Binzhou, China

Myxoid liposarcoma (MLPS) typically occurs in the extremities. Pericardial involvement is exceptionally rare and usually represents metastatic disease. Non-specific imaging features often lead to confusion with benign lesions and diagnostic errors. This report describes a 69-year-old woman presented with chest tightness and had a prior history of gluteal MLPS. Multimodal imaging (CT, ultrasound, MRI) revealed a pericardial mass. Although features such as well-circumscribed margins and delayed contrast filling suggested a benign lesion suggested a benign-leaning differential rather than a definitive diagnosis, the clinical history highly favored metastatic MLPS. Imaging could not provide a definitive diagnosis, highlighting the challenge of overlapping features between benign and malignant cardiac masses. The final diagnosis relied on histopathology and molecular testing. Postoperative immunohistochemistry indicated a spindle cell tumor with myxoid stroma (S-100 negative, MDM2 weakly positive). Molecular pathology confirmed the diagnosis by detecting the FUS-DDIT3 fusion gene, establishing metastatic MLPS. This case underscores the critical limitations of imaging in reaching a definitive diagnosis and emphasizes that accurate classification necessitates integration with histopathological and molecular analyses. An optimized diagnostic strategy should incorporate a comprehensive review of clinical history—especially any prior sarcoma—maintain heightened vigilance for overlapping imaging features of rare sarcomas in atypical locations, and include molecular pathology to effectively prevent misdiagnosis.