This 68 year-old male patient presented with cough and dyspnoea. The PA chest xray above shows a veil-like opacity in the left upper zone, and silhouetting of the left heart border, typical of left upper lobe collapse. The trachea is shifted to the left and there is a small juxtaphrenic peak. The luftsichel sign is present due to the superior segment of the left lower lobe insinuating itself between the collapsed upper lobe and the mediastinum (click image for arrows). The lateral film shows anterior displacement of the oblique fissure, with a prominant bulge in the hilar region suggesting a mass. This patient did indeed have a hilar carcinoma causing obstruction of the left upper lobe bronchus.

Around 50% of all lung cancers exhibit some degree of atelectasis or consolidation as a result of obstruction of main, lobar or segmental bronchi. Air bronchograms may be absent due to filling of the bronchi with secretions.

Reference: Webb WR, Higgins CB. Thoracic Imaging: Pulmonary and Cardiovascular Radiology. Lippincott, Williams & Wilkins 2005
Credit: Dr Laughlin Dawes