Peribronchiolar lymphocytic infiltration

Cysts likely reflect airway obstruction caused by peribronchiolar lymphocytic infiltration (50). Peribronchovascular and subpleural cystic airspaces may be observed in up to two-thirds of patients and may progress over time (49,51,54). Honeycomb cysts are uncommon (5-20%) (49-51) but may develop in areas of prior consolidation (50). In a study of 14 patients of LIP who had serial CT scans, 9 improved, 4 worsened, and 1 remained stable (50). Many parenchymal abnormalities were reversible (50). However, cysts or architectural distortion either worsened or did not change on follow-up (50). Additional cysts often developed in areas where centrilobular nodules had been present on initial CT scans. 

Figure 6 Follicular bronchiolitis observed as an associated lesion in a patient with primary Sjogren s syndrome and a pattern of nonspecific interstitial pneumonia. The lumen is narrowed by an extensive peribronchiolar lymphocytic infiltrate. HES lOOx.

In the lungs of rats exposed to cigarette smoke, Chang et al. (2001) found the terminal bronchioles infiltrated predominantly with lymphocytes in the peribronchiolar region and a mild moderate degree of emphysema in the alveolar spaces. The terminal bronchioles also showed marked lipid peroxidation, dilatation, and peribronchiolar fibrosis. 

Acute rejection (AR) of the lung manifests pathologically as infiltration of mainly lymphocytes in the perivascular and peribronchial/peribronchiolar regions. It is graded according to the intensity of the infiltrating cells and to the extent of lung parenchyma involvement. Air space oedema and mononuclear cells are also present features. 

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