Diagnostic value of “River Sign” in focal organizing pneumonia

Organizing pneumonia (OP) is a subset of interstitial pneumonia characterized by the clinical syndrome of organizing granulation tissue within the alveoli, alveolar ducts, or bronchioles. Histopathologically, it is marked by the presence of organizing components predominantly consisting of proliferative fibroblasts within the alveolar spaces. Focal organizing pneumonia (FOP) typically manifests as solitary pulmonary nodules or masses, constituting approximately 10% to 15% of OP cases. This condition is frequently misdiagnosed as lung cancer, which can result in unnecessary interventions such as surgical resection and percutaneous biopsy. Consequently, it is imperative to identify distinguishing features between the 2 conditions prior to surgical intervention. This study introduces a distinctive computed tomography feature, termed the "River Sign," with the objective of enhancing radiologists' comprehension of FOP, thereby improving diagnostic accuracy and informing clinical management strategies.