Early recurrence of left atrial myxofibrosarcoma: A case report of a clinical and histopathologic challenge

Primary cardiac tumors are rare, with an incidence of less than 0.33%, and the majority are benign. Sarcomas account for approximately 75% of malignant cardiac tumors, while myxofibrosarcomas represent less than 5% of these cases, making them extremely uncommon. This case report was prepared following the CARE guidelines to ensure comprehensive and transparent reporting and aims to describe the diagnostic and therapeutic challenges of cardiac myxofibrosarcoma. A 60-year-old woman with no relevant medical history complained of epigastric pain, dyspnea, and diaphoresis, leading to a diagnosis of non-ST-elevation myocardial infarction. Transthoracic echocardiography revealed a heterogeneous 3.2 × 3.0 cm mass attached to the atrial side of the anterior mitral valve leaflet, which was subsequently surgically removed. Histological examination of the resected mass identified abundant fibrin, vascular proliferation, and sparse cellularity without definitive evidence of malignancy, suggesting an organized intracardiac thrombus as a differential diagnosis. Four months later, the patient developed progressive dyspnea, orthopnea, and fatigue. Further evaluation with cardiac magnetic resonance imaging revealed a recurrent 4.4 × 4.0 cm mass in the left atrium, obstructing mitral inflow. A second surgical resection and valve replacement were performed. The histopathological analysis identified polygonal and spindle-shaped myofibroblasts embedded in a myxoid stroma with scattered lymphocytes, plasma cells, and focal necrosis. Immunohistochemical staining showed focal positivity for Smooth Muscle Actin, CD34, and p53, with negative staining for h-caldesmon, myogenin, CKAE1/3, CD117, S100, calretinin, MDM2, calponin, D2-40, MyoD1, and CD31confirming the diagnosis of myxofibrosarcoma. Cardiac myxofibrosarcomas are rare but aggressive tumors with a potential for recurrence. This case highlights the diagnostic challenges posed by their atypical presentation and the risk of initial misdiagnosis. Regular follow-up using multimodal imaging, particularly cardiac magnetic resonance, is crucial for early detection and timely intervention of recurrence. A multidisciplinary approach involving cardiologists, radiologists, pathologists, and cardiac surgeons is essential to optimize diagnosis, treatment, and long-term outcomes.