The chest x-ray shows almost complete opacification of the right lung with associated volume loss. This is in keeping with complete collapse of the right lung. Potential causes are endobronchial obstruction from the tumour or mucus plugging of the right main bronchus.

Hemithorax opacification on chest x- ray can be due to 4 causes:

• Collapse of entire lung – mediastinal shift towards the white out.
• Massive pleural effusion – mediastinal shift to the opposite side.
• Consolidation involving entire lung – no mediastinal shift.
• post pneumonectomy – mediastinal shift towards the affected side with volume loss; surgical clips visible.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2802710/