Lung lesions

IgG4-related lung lesions are characterized by inflammatory cell infiltration and fibrosis occurring in the connective tissue (lymph tract) within the lung, mainly along the bronchovascular bundle, interlobular septa, and alveolar interstitium. As a result, diagnostic imaging studies often reveal ground-glass opacities and thickening of bronchovascular bundle and interlobular septa. In addition, some cases demonstrate mass lesions that must be differentiated from primary lung cancer. Classification into four types on the basis of CT findings is possible: (1) solid, nodular lesions; (2) rounded ground-glass opacities (GGO); (3) alveolar-interstitial lesions; and (4) a bronchovascular pattern. Each of these types must be differentiated from other disorders that can present with similar radiologic findings. Comprehensive diagnosis must also consider the serum IgG4 concentration; the presence or absence of other organ involvement; and, whenever possible, the pulmonary histopathology.