Histologic changes: At low power, parts of three lobules are separated by interlobular septa. Within the lobule, an inflammatory infiltrate is present in and around the distal airways and here and there in the alveolar parenchyma. Inflammation tends to spare the interlobular septa and pleura. There is no overall distortion of architecture. What diseases cause this type of distribution? Answer

A

The patchy inflammation corresponds to the micronodules seen on CT, and confluent areas of infiltrate correspond to ground glass attenuation.

At higher magnification (B), a cellular bronchiolitis and patchy alveolitis with mild widening of alveolar walls and alveolar filling are present.

B

TB = Terminal bronchiole, RB = Respiratory bronchiole, AD = Alveolar duct

Clinical summary Image 2

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A. Diseases that give this histologic pattern include: