Thymoma with intravascular extension into the right atrium.

Figure 1: Computed tomography (CT) scan of the chest. Axial image (A) shows a 2 × 3 cm mass in the anterior mediastinum and a tumour thrombus occluding the SVC and the azygos vein (arrows). On CT scan, the mediastinal mass does not have any connection either with the LBV or with the SVC. This unusual intravascular growth is due to the spread of the tumour into the LBV and SVC through the thymic veins, similar to some renal cell carcinomas extending via the renal vein and the inferior vena cava into the right atrium. Coronal image (B) clearly shows the intravascular extension of the mediastinal tumour into the SVC (arrow) and the right atrium.