Pseudolesion of the chest. A conglomerate shadow on the lateral radiograph.

A pseudolesion encountered in the lateral chest roentgenogram of normal patients is described. This concatenation of shadows can produce an opacity which projects over the distal aortic arch and can simulate a mass or pneumonia. This pseudolesion can be found in 4 to 5 percent of normal lateral chest films and is formed by superimposition of normal upper lobe vascular structures.