Intraluminal fibrosis in interstitial lung disorders

Area of Science:

• Pulmonary pathology
• Interstitial lung diseases
• Histopathology

Background:

• Interstitial lung diseases (ILDs) exhibit diverse histopathologic features.
• Intraluminal organizing and fibrotic changes are recognized but their pathogenesis requires elucidation.
• Understanding these intraluminal changes is crucial for diagnosing and managing ILDs.

Purpose of the Study:

• To investigate the histopathologic and ultrastructural features of intraluminal organizing and fibrotic changes in various interstitial lung disorders.
• To identify distinct patterns of intraluminal changes and explore their common pathogenetic mechanisms.
• To correlate specific patterns with different ILD subtypes.

Main Methods:

• Analysis of open lung biopsies and autopsy specimens from 373 patients with diverse interstitial lung disorders.
• Histopathologic and ultrastructural examination to characterize intraluminal changes.
• Classification of observed patterns into intraluminal buds, obliterative changes, and mural incorporation.

Main Results:

• Three distinct patterns of intraluminal organization and fibrosis were identified: intraluminal buds, obliterative changes, and mural incorporation.
• A common pathogenetic mechanism involving migration of activated connective tissue cells into the intraluminal compartment was suggested.
• Intraluminal buds were frequent in hypersensitivity pneumonitis and chronic eosinophilic pneumonia.
• Mural incorporation and obliterative changes were prominent in idiopathic pulmonary fibrosis and other ILDs, playing a role in pulmonary remodeling.

Conclusions:

• Intraluminal organizing and fibrotic changes in ILDs share a common pathogenetic pathway.
• Specific patterns of intraluminal changes are associated with particular ILD subtypes.
• These intraluminal processes significantly contribute to pulmonary remodeling and alveolar fusion in ILDs.