Lesions in resected lung parenchyma with regard to possible initial phase of pulmonary emphysema. An ultrastructural study.

Lung tissue appearing macroscopically normal and remote from pathological lesions was examined in semithin and ultrathin sections of surgically excised lobes or entire lungs of 14 patients. Thin areas and apertures were found occupying some of the intercapillary areas of alveolar septa. Thin areas differ from normal intercapillary areas both by their lesser mean thickness and structure; collagenous and elastic fibers, processes of fibrocytes and intercellular substance are absent. Either two layers or only one layer of epithelial lining are encountered in such thin areas. Septal apertures correspond mostly to pores of Kohn by their dimensions. Only some exceed these dimensions or appear in a higher amount per length unit of the alveolar septum. In accordance with other authors we believe that both the thin portions and the apertures of alveolar septa could represent an early phase of destruction in initial stages of pulmonary emphysoma. Continuous epithelial lining in two emphysematous bullae is presented. Structurally, the lining cells are similar to type 2 alveolar epithelial cells, but their bronchiolar origin also has to be considered.