Figure 2. 42-year-old man with pulmonary Wegener's granulomatosis. A coronal CT reformatted image of the chest shows a peripheral pulmonary mass, with early cavitation (arrow). There is a background mosaic pattern of lung attenuation, thought to be due to a mosaic perfusion abnormality caused by a primary vascular abnormality rather than ground-glass attenuation caused by air trapping.