Fig. 17
From: Clinical and radiological features of idiopathic interstitial pneumonias (IIPs): a pictorial review
Pattern of LIP. Small thin-walled cysts (white arrows) represent a typical imaging feature of LIP, usually not exceeding 30 mm and located in the mid-lung zones, adjacent to blood vessels. A partial “check-valve” bronchiolar obstruction has been considered the main explanation for cyst formation. The bronchiolar obstruction—due to lymphoid nodules and aggregates—leads to “air trapping”