Areas of atypical epithelial proliferation were seen in the terminal airspaces in eight cases of
idiopathic diffuse interstitial pulmonary fibrosis. These atypical changes included the
presence of cuboidal and columnar epithelium characteristic of more proximal airspaces,
squamous metaplasia in areas of predominantly cuboidal or columnar cells, and
stratification of cells at times to a marked degree. In some areas nuclear and cytoplasmic
changes suggested progression toward frank malignancy. Lung cancer was present in three …