What is this appearance known as?
"Golden S sign" or "reverse S sign of Golden"
What is the lucency between the trachea and the collapsed right upper lobe due to? What is the equivalent on the left known as?
Hyperinflation of the right lower lobe interposed between the collapse right upper lobe and the mediastinum. This usually does not occur on the right; presumably on this occasion it is due to the right hilar mass. On the left it is known as Luftsichel sign.
Chest x-ray demonstrates increased density in the upper medial hemithorax with loss of volume, and shift of the trachea to the right. A mass is present at the right hilum.