THE PATHOLOGIST'S APPROACH TO THE DIAGNOSIS OF IDIOPATHIC PULMONARY FIBROSIS (IPF)

In approximately 70% of patients, the fibrosis is most severe in the lower lung zones, in about 20% of patients all zones are involved to a similar degree, and in about 10% of patients mainly the middle or upper lung zones are involved. 17,18 Honeycombing and fibrosis are most often symmetrical, but asymmetry may be present. In the vast majority of patients with IPF, serial HRCT scans show an increase in the extent of reticulation and honeycombing. 19-21 This progression usually occurs gradually over several months or years. Occasionally patients develop a fulminant and oftenfatal acute exacerbation. 22,23 HRCT findings consist of extensive multifocal, peripheral or diffuse groundglass opacity superimposed on a background of interstitial fibrosis. 24,25 This appearance correlates with the presence of diffuse alveolar damage on lung biopsy. 24,25