Architectural Distortion

Traction bronchiolectasis: Inflamed alveoli (alveolitis) often collapse and do not reexpand. As a result of alveolar collapse, bronchioles and small bronchi dilate. Note the dilated bronchiole (B), respiratory bronchiole (RB), and alveolar duct (AD). The pleura is at the lower left. When collapse is more severe and all alveoli become obliterated, the dilated airways become honeycombed spaces with thick walls (see below).

Honeycombing

These enlarged air spaces have thick walls and are lined by respiratory epithelium (honeycombing). One space near the bottom is filled with exudate (E). The surrounding fibrous tissue has bundles of metaplastic smooth muscle (arrow) and a moderate lymphoid inflammatory infiltrate. The slightly thickened pleura lies to the left.

Another common finding

Besides smooth muscle metaplasia, other types of metaplasia occur in the chronically inflamed connective tissue. What is the metaplasia shown here? Answer

Clinical summary Discussion

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Answer: This is bony metaplasia. Note the fatty marrow in the center. This finding is common but has no clinical significance.

Clinical summary Discussion

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