The initial pathologic descriptions of these airway alterations in emphysema highlighted the importance of two features: inflammation as a mechanism, and respiratory bronchioles as the primary site of involvement.
Histopathologic Features of Chronic Obstructive Pulmonary Disease Emphysema Proximal acinar emphysema * Destruction of respiratory bronchioles with relative sparing of distal alveoli Panacinar emphysema * Destruction of respiratory bronchioles through to terminal alveoli Alteration of Respiratory (smoker's) bronchiolitis the airways Inflammation and fibrosis of terminal and respiratory bronchioles Reduction in terminal bronchioles Goblet cell metaplasia Squamous metaplasia Alteration of Intimal thickening with smooth muscle the vasculature proliferation and elastin/collagen deposition Smooth muscle hyperplasia of the media
(9) However, studies based on lung cancer resection specimens have shown that fine fibrosis in the alveolar walls around respiratory bronchioles is in fact very common in the lungs of cigarette smokers who have no clinical evidence of an ILD.
Yousem et al (8) found "thick fibrous septa" around the respiratory bronchioles in some of their RBILD cases, a description that fits RBF.
In primates, lymphatic vessels exist at the alveolar level adjacent to the respiratory bronchioles (20,21).
In the low-dose miners, the interstitial compartments with the greatest amount of particulate material were the interlobular, intersegmental, and perivascular connective tissue; the alveolar and alveolar duct septa; the interstitium of respiratory bronchioles; and the pleura.
In this paper, we report evidence that both carbonaceous and mineral dust are primarily distributed to the terminal and respiratory bronchioles
and that there is anatomical remodeling within these same sites.
(29,100-126) The term diffuse panbronchiolitis refers to its distribution in both lungs (diffuse) and the inflammatory involvement of all layers of the wall or respiratory bronchioles
Grading of Severity of Fibrosis for Asbestosis Cases Grade 0 No appreciable peribronchiolar fibrosis, or less than half of bronchioles involved Grade 1 Fibrosis confined to the walls of respiratory bronchioles
and the first adjacent tier of adjacent alveoli, with involvement of more than half of all bronchioles on a slide Grade 2 Extension of fibrosis to involve alveolar ducts and/or 2 or more tiers of alveoli adjacent to the respiratory bronchiole
, with sparing of at least some alveoli between adjacent bronchioles Grade 3 Fibrotic thickening of the walls of all alveoli between at least 2 adjacent respiratory bronchioles
Grade 4 Honeycomb changes Table 2.
In the original article of Myers et al, (1) the major pathologic finding was the presence of RB: clusters of slightly golden colored alveolar macrophages ("smoker's macrophages") in the lumens of respiratory bronchioles
, alveolar ducts, and in the surrounding alveoli.
The stellate lesions are small, discrete, and centered around respiratory bronchioles
and adjacent small arteries, with intervening uninvolved lung parenchyma present.
We also describe the surprising finding of fibrotic lesions of the large bronchi, which is usually restricted to membranous and respiratory bronchioles
, in the context of chronic rejection with OB.