Pathologic manifestations of Immunoglobulin(Ig)G4-related lung disease

Immunoglobulin(Ig)G4-related disease (IgG4-RD) is a fibroinflammatory condition that can affect virtually any organ and usually presents as tumefactive lesions involving multiple sites. Characteristic histopathology of IgG4-RD consists of dense lymphoplasmacytic infiltrate, fibrosis (often in storiform pattern), and obliterative phlebitis, accompanied by tissue infiltration of IgG4-positive plasma cells with or without elevation of serum IgG4 level. Despite a general similarity in the morphologic manifestations of IgG4-RD, site-specific unique morphologic features have been described in some organs including the lung. Compared with other sites, pulmonary involvement by IgG4-RD has been recognized more recently, and lung biopsy interpretation for this condition is often challenging, as both a relative paucity of pathognomonic features and a plethora of overlapping findings with other fibroinflammatory processes of the lung. This review is focused on the morphologic spectrum of IgG4-related lung disease documented in the current literature and on the pertinent issues in the differential diagnoses with other conditions encountered in the lung. (C) 2012 Elsevier Inc. All rights reserved.