Invasive Development of Right Atrial Myxoma— A Case Report

A thirty-nine-year-old man was admitted to the authors' department complaining of exertional dyspnea and high fever. An echocardiogram showed a mass in the right atrium, which was observed to move to the right atrium during the systolic phase and to the right ventricle during the diastolic phase. Magnetic resonance imaging showed that the mass developed from the right atrium to the superior vena cava. Intravenous digital subtraction angiography also showed a partial defect of the right atrium as well as obstructions of both the superior vena cava and the bilateral innominate veins. A pulmonary hemodynamic scintigram showed multiple defects at the mid and inferior areas of each lung, suggesting multiple pulmonary infarctions. The right atrial tumor was surgically removed. The superior vena cava and the innominate veins were found to be obstructed by organized thrombi, and the tumor had invasively grown into the right atrial wall. Histologic findings demonstrated that most of the tumor was composed of organized thrombi with scattered myxomatous tissue and was diagnosed as cardiac myxoma. These histologic findings suggest that the histogenesis of this right atrial myxoma might be thrombogenic.