RESUMEN
BACKGROUND Tumor embolism is a rare neoplastic complication that occurs when there is intravenous invasion by a benign or malignant tumor. We present the case of an asymptomatic patient with an incidentally discovered leiomyosarcoma tumor emboli, which was initially misdiagnosed as "thrombus in transit." CASE REPORT The patient was a 58-year-old woman who was incidentally found on echocardiogram to have a large tubular mass within the inferior vena cava and right atrium. Although initially characterized as "thrombus in transit", this mobile right atrial mass was present without clinical, echocardiographic, or radiographic evidence of pulmonary embolism or increased pulmonary arterial impedance. Given that a thrombus in transit is nearly always associated with submassive or massive pulmonary emboli and their attendant right heart sequelae, these pertinent negative findings led us to seek an alternative diagnosis. After a trial of conservative management with anticoagulation and attempted removal of the mass with the AngioVac system, the patient ultimately underwent median sternotomy and surgical embolectomy on cardiopulmonary bypass to remove the mass, which was later identified on pathology as a leiomyosarcoma. CONCLUSIONS With rare exceptions, "thrombus in transit" is accompanied by large pulmonary emboli and the presence of increased pulmonary artery pressure and right heart strain. The absence of clinical, echocardiographic, or radiographic evidence of these hemodynamic sequelae should raise suspicion for an alternative diagnosis. Tumor embolism should be considered in the differential diagnosis of any patient with a history of malignancy who presents with evidence of intracardiac mass or embolism.