Primary Malignant Mesenchymal Sarcoma of the Left Atrium Complicated with Mitral Valve Disease: A Case Report

Abstract Primary cardiac malignant tumors are extremely rare, accounting for less than 0.05% of all cardiac tumors, with malignant mesenchymal sarcomas being one of the most aggressive subtypes. Herein, we report a case of a 56-year-old female patient admitted with acute chest distress and dyspnea, initially suspected of left atrial myxoma combined with moderate mitral stenosis. The patient underwent minimally invasive cardiac surgery under cardiopulmonary bypass, including mitral valve replacement and tumor resection, but converted to thoracotomy due to intraoperative hemorrhage. Postoperative pathological and immunohistochemical examinations confirmed the diagnosis of malignant mesenchymal sarcoma. Severe complications including low cardiac output syndrome, acute respiratory distress syndrome (ARDS), and acute kidney injury occurred postoperatively, which were successfully managed with comprehensive supportive treatments. This case highlights the challenges in preoperative diagnosis, surgical management, and postoperative complication control of primary cardiac malignant sarcomas, and emphasizes the importance of multidisciplinary team (MDT) collaboration in improving patient outcomes.​