The morphology of alveolar tissue destruction.

Destruction of intra-alveolar stroma in regions of tuberculous pneumonia is described. This destruction is associated with phagocytosis of argentophilic granules and fibre fragments by macrophages. The specific features of stromal destruction consist of sequestration, fragmentation, lysis, and other, less obvious, changes in reticulin and collagen fibres found in the air spaces. These findings have important implications in chronic fibrosing pneumonitis where similar intra-alveolar stromal changes occur. Destructive stromal changes have also been noted within granulomatous nodules of sarcoidosis in the region of giant cells. Some of the latter also contain argentophilic fibre fragments.