Cryptogenic Organizing Pneumonia Presenting as a Solitary Mass: Clinical, Imaging, and Pathologic Features

BACKGROUND Cryptogenic organizing pneumonia (COP), with a variety of radiologic findings, is a clinical pathological entity characterized by the presence of granulation tissue composed of fibroblasts/myofibroblasts and loose connective tissue in the alveoli and/or the distal bronchioles. Nevertheless, the presence of a solitary mass in COP is relatively rare. This study investigated the clinical, imaging, and pathologic features of COP with solitary mass form. MATERIAL AND METHODS This retrospective analysis included 12 patients (9 men and 3 women; age range 36-78 years; mean age 60±9 years) with surgery- or biopsy-proven COP with a solitary lung mass, diagnosed between June 2012 and December 2017 at the Department of Radiology in our hospital. RESULTS All patients experienced cough with expectoration and 8 patients had hemoptysis. All lesions were adjacent to the pleura. Mean size of the lesions was 4.2±0.9 cm (range, 3.2-6.1 cm). The upper left lobe was the site of the lesion in 4 patients. Six masses had heterogeneous density; among these, 4 had cavities and distal obstructive inflammation. The mass caused pleural indentation in 4 patients. Lymphadenopathy was seen in 7 patients. All specimens showed buds of granulation tissue within the lumen of the distal pulmonary airspaces, with significant increase in interstitial lymphocytes in 4 specimens. CONCLUSIONS Patients with COP with solitary mass form are more susceptible to hemoptysis and the mass is prone to necrosis. Vascular bundles, exudation around the mass, interstitial lymphocyte infiltration, and mediastinal lymph node enlargement are common features.