Bronchiolitis obliterans-organizing pneumonia (BOOP)-like variant of Wegener's granulomatosis. A clinicopathologic study of 16 cases.

The classic histologic features of Wegener's granulomatosis (WG) in lung include necrotizing granulomatous inflammation and necrotizing vasculitis. Recently, several histologic variants have been recognized, including cases characterized by bronchocentric inflammation, a marked eosinophil infiltrate, alveolar hemorrhage, and capillaritis or interstitial fibrosis. We report 16 cases of another variant in which bronchiolitis obliterans-organizing pneumonia (BOOP)-like fibrosis represents the main histologic finding. The extensive geographic necrosis characteristic of Wegener's granulomatosis was absent in all cases, although small suppurative granulomas, minute foci of bland necrosis, and microabscesses were common. All cases showed the typical necrotizing vasculitis of Wegener's granulomatosis. Other frequent findings included darkly staining multinucleated giant cells, prominent acute inflammation, aggregates of epithelioid histiocytes, hemosiderin-filled macrophages, and areas of nonspecific parenchymal fibrosis. The clinical and radiographic features of this variant of Wegener's granulomatosis appear to be indistinguishable from the classic type. Pathologists need to be aware that Wegener's granulomatosis can occasionally manifest histologic changes suggestive of BOOP. The diagnosis will not be overlooked if additional features, especially vasculitis, suppurative granulomas, tiny necrotic zones, microabscesses, and multinucleated giant cells, are appreciated.