The many faces of cryptogenic organizing pneumonia (COP).

Organizing pneumonia (OP) is interstitial pneumonia with an acute or subacute clinical course and a histological pattern compatible with acute lung injury. It usually arises after a recent infection of the peripheral bronchial system, whereby is called secondary OP. However, often OP arises with no recognizable cause for which it is called cryptogenic organizing pneumonia (COP). From a radiological standpoint, COP exhibits different imaging appearances and this review makes radiologists and clinicians familiar with the entire spectrum of expected disease findings. Successful interpretation of imaging is pertinent for a rapid diagnosis of COP and knowledge of the entire spectrum of imaging findings in COP is mandatory.