The patient tested positive only for rhinovirus. Bronchoscopy demonstrated a mucus plug in the right middle lobe bronchus and no tumor. Follow-up CXR the next day was normal.

The signs of right middle lobe collapse and consolidation are subtle. As a differential diagnosis in an asymptomatic patient consider pectus excavatum which also causes poor definition of the right heart border and increased opacity in the right lower zone. However, in pectus excavatum, the heart would be displaced to the left, and the anterior ribs would be more vertically oriented. 

Radiographic interpretation requires a thorough examination of the image and a thorough knowledge of normal appearances. The CXR is a puzzle to be solved. Everything between the anode and the detector is superimposed on the image. This is the ultimate in volume averaging, and the degree of blurring or clarity depends on the orientation of interfaces with respect to the X-ray beam. 

Lastly, note how subtle the lower zone opacity is on X-ray compared to the CT scan which benefits from superior contrast resolution and minimal volume averaging.