Collaborative radiologic and histopathologic assessment of fibrotic lung disease.

The idiopathic interstitial pneumonias (IIPs) are a seemingly disconnected collection of diseases usually associated with the presence of pulmonary fibrosis. Categorization of the IIPs continues to be problematic despite recent attempts to refine the diagnostic criteria and suggests that rather than separate diseases, these pneumonias represent a spectrum of injury and abnormal repair of the alveolar wall. Although the initiating injury or injuries are unknown, the IIPs share a restricted number of final common abnormal pathways that lead to volume loss and lung distortion. The pathways include (a) alveolar collapse, (b) incorporation of fibroblastic material into alveolar walls, and (c) cigarette smoke-related inflammation and fibrosis. A collaborative diagnostic process in which data from radiologic and histologic assessments are combined allows a more reliable identification of the predominant pathways leading to pulmonary fibrosis. This approach has implications for therapy and the future direction of research.