Prominence of the pulmonary outflow tract on the lateral view and fullness in the AP window on the frontal view, which could represent a range of conditions including pulmonary artery enlargement, elevated pulmonary artery pressure, abnormal pulmonic valve, idiopathic pulmonary artery dilatation, or a mediastinal lesion.
Enlarged pulmonary artery (Uncertain) Superior mediastinal mass (Uncertain)