A 69-year-old woman presented as an outpatient with shortness of breath. She was a former smoker and had a past medical history of rheumatic heart disease with mild mitral stenosis and moderate-to-severe mitral insufficiency associated with atrial fibrillation. A chest x-ray revealed near-complete opacification of the right mid-to-lower lung zones, with a shift of the mediastinal structures and heart leftward (Figure 1). A mass lesion was suspected. Computed tomography (CT) was performed without …