An unusual finding in the right atrium

Clinical introduction A 66-year-old asymptomatic patient underwent a routine transthoracic echocardiogram prior to commencement of clozapine, and was found to have a mobile echogenic structure in the right atrium, which was later confirmed on transoesophageal echocardiogram to be adjacent to the insertion of inferior vena cava. Follow-up cardiovascular MRI (CMR) revealed a mobile, avascular 2.1×2.2 cm 2 mass with regular and smooth borders, adjacent to the eustachian valve (Figure 1 panel A: coronal view; online supplementary movie 1). Late gadolinium enhancement (LGE; panel B) demonstrated heterogeneity, and T1-imaging demonstrated mild hyperintensity (panel C). There was no evidence of obstructive haemodynamic compromise. The mass was subsequently resected, and the histology (H&E staining, magnification ×100) is shown in panel D. Question The diagnosis of this mass is: Aberrant liver Angiosarcoma Atrial myxoma Renal cell carcinoma Thrombus