Pathology in the diagnosis of interstitial lung diseases

Interstitial lung diseases (ILDs) encompass a wide spectrum of pulmonary diseases associated with variable clinical presentation, treatment response and prognosis that represent a real challenge for diagnosticians. Until the publication of the 2002 consensus paper by the American Thoracic Society and European Respiratory Society (1), histopathological examination was regarded as the gold standard in diagnosing and classifying idiopathic ILDs. This approach was supported by the notion that histopathology allowed better separation of different ILD entities than the high resolution computed tomography (HRCT) patterns seen by radiologists. However, in clinical practice diagnostic accuracy of ILD among expert clinicians, radiologists and pathologists working in diagnostic isolation varied considerably and was associated with a poor inter-observer agreement. In recognition of these diagnostic difficulties, the use of an interactive approach between experienced clinicians, radiologists and pathologists significantly improved diagnostic accuracy as well as overall confidence in the final diagnosis (2). Since then this multidisciplinary team (MDT) diagnostic approach has been recommended in multiple consensus statements and currently represents the cornerstone in optimizing the diagnosis of ILDs, including usual interstitial pneumonia/idiopathic pulmonary fibrosis (UIP/IPF) (1-3). These guidelines support the concept that in the appropriate clinical context, HRCT patterns of definite or probable UIP are sufficient to provide a confident diagnosis of IPF without histopathological confirmation. In a recently published update on the diagnosis of IPF by the Fleischner Society, the expert panel recommended that histopathological examination of a surgical lung biopsy (SLB) should be considered if the clinicalradiological picture is indeterminate or inconsistent with UIP (4). It should be emphasized, however, that equal radiological and pathological patterns occur in ILDs secondary to collagen vascular diseases, intake of drugs or environmental exposures