Among the Masses: Multiple Left Atrial Undifferentiated Pleomorphic Sarcomas.

Undifferentiated pleomorphic sarcoma, an exceedingly rare and aggressive primary cardiac tumor arising from mesenchymal stem cells, is associated with poor prognosis and high mortality despite adequate treatment. A 52-year-old female presented with a 2-month history of angina and dyspnea on exertion. Her clinical history included severe acute respiratory syndrome coronavirus 2 myocarditis and iron deficiency anemia. Elevated troponin 1 and D-dimer prompted further investigation, and diagnostic imaging revealed multiple hypodensities in the left atrium and a right-sided pleural effusion that were causing severe mitral stenosis and pulmonary hypertension. Full body positron emission tomography scan suggested metastatic disease, prompting surgical resection of the atrial masses. Pathology confirmed high-grade undifferentiated pleomorphic sarcoma. Treatment with chemotherapy resulted in clinical stability without radiographic evidence of recurrence at 9 months. At follow-up >2 years after the initial diagnosis, echocardiogram demonstrated normal left ventricular systolic function with ejection fraction of 55% to 60%, no mitral gradient, and resolution of pulmonary hypertension. Left atrial masses are a diagnostic challenge because of the location and the technical difficulty of biopsy. Undifferentiated pleomorphic sarcoma has a 5-year survival rate of approximately 60%, so the condition necessitates prompt diagnosis and treatment.