Pathology of IPF

Abstract

The pathological pattern of usual interstitial pneumonia (UIP) is defined as temporal and topological heterogeneous chronic interstitial pneumonia with a peripheral lobular distribution. The natural history of UIP is unclear, but attempts have been made to elucidate it. The complication of acute and subacute worsening or exacerbation has been discussed as an important part of the natural history of UIP. The major differential diagnoses of UIP are nonspecific interstitial pneumonia, desquamative interstitial pneumonia, and airspace enlargement with fibrosis. In a significant number of cases, analyses of pathological materials have just led to a diagnosis of chronic interstitial pneumonia not otherwise specified (an important component of unclassifiable interstitial pneumonia). Various diseases and other factors cause UIP, including idiopathic, collagen vascular diseases; chronic hypersensitivity pneumonia; occupational exposure, especially to asbestos; and the administration of certain drugs. The role of pulmonary pathologists is to make a pathological diagnosis of UIP or another diagnosis and to look for etiological findings, like epithelioid cell granuloma and asbestos bodies. In this chapter, recent pathological advances in UIP are critically discussed, and I consider the reason why the pathological classification of IIPs varies among pathologists.