Organizing Pneumonia as a Histopathological Term

Abstract

OBJECTIVES: Organizing pneumonia (OP) is an interstitial lung disease characterized by granulation tissue buds in alveoli and alveolarductus, possibly accompanied by bronchiolar involvement. Histopathologically, OP may signify a primary disease and be observed as acontiguous disease or as a minor component of other diseases. In this study, the clinical significance of histopathological OP lesions andclinical and radiological features of patients with primary OP were examined.MATERIAL AND METHODS: Between January 2011 and January 2015, of 6,346 lung pathology reports, 138 patients with OP lesionswere retrospectively evaluated. According to the final diagnoses, patients were grouped as reactive OP (those with final diagnosis otherthan OP) and primary OP (those with OP). Patients with primary OP were classified according to etiology as cryptogenic and secondaryOP. Radiological evaluation was conducted within a categorization of “typical,” “focal,” and “infiltrative.”RESULTS: Of 138 patients, 25% were males and the mean age was 54±14 years. Pathologically, 61% of patients had reactive OP and39% had primary OP. All reactive OP lesions were reported using surgical specimens, and the most frequent primary diagnoses weremalignancy (65%), infection (15%), interstitial lung diseases other than OP (7%), and bronchiectasis (5%). Other diagnoses included bullae,foreign body, hamartoma, bronchogenic cyst, and bronchopleural fistula. Of all the primary OP patients, 48 had cryptogenic OP andsix had secondary OP. Radiological involvement was consistent with typical OP in 30%, focal OP in 63%, and infiltrative OP in 7% ofthe patients. All focal OP lesions were defined using surgical resections. Positron emission computed tomography (PET-CT) was recordedin 28 patients. In 11 patients, lymphadenomegaly was comorbid. The mean widest diameter of focal opacity was 2.7±1.2 (1.2-4.9) cm,and the mean the maximum standardized uptake value (SUVmax was 6.1±3.9 (1.7-16.7).CONCLUSION: OP lesions generally present as a minor component of other diseases. In patients with OP, cryptogenic OP and radiologicalfocal OP is more frequently observed. Most focal OP lesions are detected using surgical resections because of malignant prediagnosisowing to elevated SUVmax.