Purpose: The present study investigated chest computed tomography (CT) patterns and lung histological features, as well as the consistency between radiological and histological features among patients with microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic GPA (EGPA). Materials and Methods: The medical records of 74 antineutrophil cytoplasmic antibody-associated vasculitis (AAV) patients with radiological lung parenchymal lesions were reviewed along with the histological results for 28 of them. Chest CT patterns were divided according 12 items mostly suggested by radiologists and histological features were divided according to necrotising granuloma, necrotising vasculitis, eosinophilic infiltration, and hemosiderin laden macrophages as defined by a pathologist. Results: The mean age was 57.1 years (22 men). The most common clinical manifestation other than lung manifestation was renal manifestation (62.2%), and the most common chest CT pattern was lung involvement of vasculitis (35.1%). In MPA patients, the major histological features were hemosiderin-laden macrophages in the alveolar space and vasculitis. In GPA patients, the major histological features were necrotizing vasculitis and necrotizing granuloma, while in EGPA patients, the major histological feature was only necrotising vasculitis. The consistency rate in GPA patients was the highest (100%), followed by that in MPA patients (66.7%) and EGPA patients (50.0%). Conclusion: When lung involvement of AAV is suspected on chest CT, lung biopsy should be recommended for the proper classification of AAV, due to the discordance rate between radiological and histological findings in MPA and EGPA patients, but not GPA patients.
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