RESUMO
The discovery of a mass in the right atrium obliges the clinician to perform a broad differential diagnosis between a primary cardiac tumour (with myxoma being the most frequent), invasion of an extracardiac tumour, vegetations on the tricuspid valve, and an atrial thrombus. We describe the case of a patient who was admitted to our service with a diagnosis of suspected myxoma based on the chance transthoracic echocardiographic discovery of a right atrial mass. A transesophageal echocardiogram showed the process to be extracardiac, and magnetic resonance imaging showed it to originate at the renal level extending via the inferior vena cava to the right atrium. Tumour extension with thrombosis of the vena cava is a relatively frequent complication of renal carcinoma, but only exceptionally does it reach the right atrium. It is also exceptional that this was a chance finding in an asymptomatic patient.