Bronchocentric granulomatosis is characterized by destructive, necrotizing bronchocentric and bronchiolocentric inflammation. Early lesions show partial epithelial erosion and replacement of the airway wall by epithelioid histiocytes around the lumen. More advanced lesions may show occasional presence of granulomas. Multiple causes have been associated with this histologic lesion, including infectious and noninfectious causes. It is thought that noninfectious cases represent an allergic response to the presence of aspergillus. The inflammatory process centers on the airways. There may be some secondary inflammation involving adjacent vessel walls. Primary vasculitis with necrosis of vessel walls is not seen, and vascular involvement is usually secondary to inflammation of airways in the vicinity.

In all cases, a series of special stains and cultures for microorganisms should be obtained. In biopsies from patients with allergic bronchopulmonary aspergillosis, nonviable hyphal fragments may be found in the lumen of some airways. The differential diagnosis should include primary vasculitis (Wegener granulomatosis, Churg-Strauss angiitis), aspiration pneumonia, and rheumatoid nodules.