[A case of IgG4-related inflammatory pseudotumor of the lung].

The chest X-ray film and computed tomography of a 62-year-old asymptomatic man showed bilateral multiple nodules. Since bronchoalveolar lavage and transbronchial lung biopsy revealed no diagnostic findings, video-assisted thoracic surgery (VATS) was performed. The VATS specimens showed marked infiltration of inflammatory cells, intraluminal organization and fibrosis in the alveolar wall. Plasma cells were predominant components of infiltrating inflammatory cells. Since immunohistochemical staining of the specimens revealed much IgG4-positive plasma cell infiltration, we diagnosed IgG4-related inflammatory pseudotumor. One month after VATS, multiple nodules disappeared without any treatment or medication. No definite change or recurrence occurred after that. IgG4-positive plasma cells may be involved in the pathogenesis of inflammatory pseudotumor of the lung.