CT-histologic correlation of the ATS/ERS 2002 classification of idiopathic interstitial pneumonias

The American Thoracic Society and the European Respiratory Society 2002 classification defines the histologic patterns that provide the basis for a clinico-radiologic-pathologic diagnosis of an idiopathic interstitial pneumonia. Idiopathic pulmonary fibrosis is the clinical term for usual interstitial pneumonia, the characteristic histologic pattern is interstitial fibrosis with temporal heterogeneity, and the radiologic pattern is basal and subpleural areas of ground-glass and reticular attenuation and honeycomb pattern. Nonspecific interstitial pneumonia has cellular or fibrosing patterns of chronic inflammation with temporal homogeneity; the radiologic pattern is subpleural and basal areas of ground-glass and reticular attenuation. Lymphoid interstitial pneumonia results from lymphocyte interstitial infiltration; CT demonstrates ground-glass attenuation and nodular interlobular septal thickening. Respiratory bronchiolitis-associated interstitial lung disease is characterized by bronchiolocentric alveolar macrophage accumulation; CT shows centrilobular ground-glass attenuation. Desquamative interstitial pneumonia is characterized by alveolar macrophage accumulation with predominantly lower zone ground-glass attenuation seen on CT scans. Cryptogenic organizing pneumonia is characterized radiologically by peribronchial ground-glass attenuation and subpleural consolidation. Acute interstitial pneumonia is the clinical term for idiopathic diffuse alveolar damage; the exudative phase is characterized radiologically by diffuse ground-glass attenuation and dependent consolidation, with the additional feature of lung architectural distortion in the organizing phase. Ideally, diagnosis of an idiopathic interstitial pneumonia should be rendered only after all clinico-radiologic-pathologic data have been reviewed.