Case Report Cryptogenic organising pneumonia: clinical, pathological, and prognostic analysis of 27 cases

Background: Buds of granulation tissue within the lumen of distal pulmonary airspaces characterises organising pneumonia (OP). This study aimed to analyse the clinical and pathological features and prognosis of patients with cryptogenic OP. Methods: Twenty-seven patients were retrospectively analysed. A multidisciplinary team (a clinician, radiologist, and pathologist) diagnosed all patients. Clinical features, laboratory data, chest radiology, treatment and prognosis, pulmonary function, and haematoxylin-eosin and immunohistochemical staining were assessed. Results: Symptoms (in decreasing prevalence) were cough, dyspnoea, fever, and chest tightness. The erythrocyte sedimentation rate (in most patients) and C-reactive protein level were increased. Radiologic findings (in decreasing prevalence) were consolidation, nodules, and band-like opacities. The lung function results were ‘normal’ and ‘restrictive’ in 30.8% and 38.5% of patients, respectively. Most patients responded to corticosteroids. The prognosis of the patients was excellent in 77.8% and poor in 22.2%. Organised polypoid granulation inflammatory tissue was in the distal bronchiole airways, respiratory bronchioles, alveolar ducts, and alveoli. Transforming growth factor (TGF)-β and alpha-smooth muscle actin (α-SMA) expression was not significantly different between the good and poor prognosis groups (P>0.05). There was increased expression of fibrin (poor prognosis group, P<0.05) and Krebs von den Lungen-6 (KL-6) (good prognosis group, P<0.05). Conclusions: Organised polypoid granulation inflammatory tissue in the distal airway spaces is a pathological feature of OP. The good and poor prognosis groups had similar expressions of TGF-β and α-SMA. Fibrin and KL-6 expression was increased in the poor prognosis group and good prognosis group, respectively.