DISCUSSION: Bronchiolar metaplasia is a reactive condition where bronchiolar epithelium extends beyond respiratory bronchioles along the alveolar septa and replaces normal alveolar lining cells. The process is known as “lambertosis” since it is thought that the metaplastic epithelium is derived from canals of Lambert which normally connect non-respiratory bronchioles to adjacent alveoli. The histopathology of bronchiolar metaplasia is an extension of columnar or ciliated epithelium beyond the alveolar ducts to the alveolar walls. When the metaplasia is extensive, it may appear as nodules measuring 2-5 mm in diameter. Lambertosis is associated with tobacco use and may be a reactive process due to chronic injury to terminal and respiratory bronchioles. The metaplasia is presumed postinflammatory in origin and may be a consequence of bronchiolitis, chronic hypersensitivity pneumonitis, bronchiectasis, or COPD.