From the radiologic pathology archives: organization and fibrosis as a response to lung injury in diffuse alveolar damage, organizing pneumonia, and acute fibrinous and organizing pneumonia.
Organization, characterized by fibroblast proliferation, is a common and nearly universal response to lung injury whether it is focal or diffuse. Despite the vast range of injurious agents, the lung's response to injury is quite limited, with a similar pattern of reaction seen radiologically and histologically regardless of the underlying cause. Although there is a tendency to divide organization into distinct entities, the underlying injury to the alveolar epithelial basement membrane is a uniting factor in these processes. This pattern of lung injury is seen in the organizing phase of diffuse alveolar damage, organizing pneumonia (OP), acute fibrinous and organizing pneumonia, and certain types of fibrotic lung disease. In addition, although organization can heal without significant injury, in some instances it progresses to fibrosis, which can be severe. When fibrosis due to organization is present, other histologic and imaging patterns, such as those seen in nonspecific interstitial pneumonia, can develop, reflecting that fibrosis can be a sequela of organization. This article reviews the histologic and radiologic findings of organization in lung injury due to diffuse alveolar damage, OP, and acute fibrinous and organizing pneumonia and helps radiologists understand that the histologic and radiologic findings depend on the degree of injury and the subsequent healing response.
From the Departments of Diagnostic Radiology and Nuclear Medicine (Chest Imaging) (S.J.K., J.R.G.) and Internal Medicine (Pulmonary/Critical Care) (J.R.G.), University of Maryland School of Medicine, 22 S Greene St, Baltimore, MD 21201; Division of Pulmonary and Mediastinal Pathology, The Joint Pathology Center, Joint Task Force National Capital Region Medical, Silver Spring, Md (T.J.F.); and Department of Chest Imaging, American Institute for Radiologic Pathology, Silver Spring, Md (J.R.G.).
Seth J
SJ
Kligerman
Teri J
TJ
Franks
Jeffrey R
JR
Galvin
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology; D055370:Lung Injury / Q000150:complications* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis* / Q000209:etiology*; D011658:Pulmonary Fibrosis / Q000175:diagnosis* / Q000209:etiology*; D014057:Tomography, X-Ray Computed / Q000379:methods*