RESULTS: A total of 9 patients with IgG4-RLD were identified, of which 8 were male and all were Caucasians. The median age at diagnosis was 64 years (interquartile range [IQR], 59-70). Serum IgG4 measurement was available in 8 patients, and the median peak serum IgG4 level was 234 mg/dL (IQR, 93-479). Five patients had respiratory symptoms on presentation, of which cough (N=4) and dyspnea (N=4) were most common, followed by nasal congestion (N=3). The main radiographic abnormality that led to biopsy was seen in the parenchyma (mass or nodule) in 7 patients, the central airway (stenosis) in 1 patient, and the pleura (pleural thickening and effusion) in 1 patient. The secondary radiographic abnormality was seen in 5 patients; 4 had mediastinal and/or hilar lymphadenopathy, and 1 had bronchial stenosis. The median count of IgG4+ cells was 65 (IQR, 49-117) per HPF, and the median IgG4+:IgG+ ratio was 0.56 (IQR, 0.47-0.74). No medical treatment was immediately necessary in 4 patients who underwent complete surgical resection of the pulmonary lesion. Among those patients; however, 3 had a recurrence of IgG4-RLD and received either corticosteroids or steroid-sparing agents during the clinical follow-up. The remaining 5 patients received corticosteroids immediately after the diagnosis of IgG4-RLD. All 5 patients subsequently developed either recurrence of IgG4-RLD or experienced the re-emergence of IgG4-related disease in the extra-pulmonary organs.