Interstitial Pneumonias

Desquamative interstitial pneumonia

Most patients are smokers. Lesions are similar to those of respiratory bronchiolitis (see below) but more diffuse.

Respiratory bronchiolitis

Fibrous scar surrounds terminal and respiratory bronchioles. Large numbers of alveolar macrophages with light brown pigment (PAS-D+) fill adjacent alveoli. More peripheral alveoli are spared.

When this lesion causes cough and dyspnea accompanied by radiographic opacities, it is known as respiratory bronchiolitis-interstitial lung disease, a rare occurrence.