Figure 4.

Usual interstitial pneumonia pattern in two patients with idiopathic pulmonary fibrosis. a) At low magnification, subpleural/paraseptal scars obscuring the alveolar architecture alternate with normal lung (“patchy fibrosis”). At the top, two areas of honeycombing can be observed (haematoxylin and eosin stain, 20×). b) At higher magnification a fibroblastic focus, consisting of a dome-shaped collection of fibroblasts/myofibroblasts embedded in a myxoid matrix and covered by hyperplastic pneumocytes, is observed. Note the pale grey colour of the fibroblastic focus, contrasting with the pink colour of the underlying scar (haematoxylin and eosin stain, 400×).