[Immunoglobulin G4-related inflammatory pseudotumor of the lung].

A 61-year-old man was pointed out a solitary nodule located in the left lung (S9) measuring 18 × 29 mm in size along with lymphadenopathy by chest computed tomography (CT). Positron emission tomography( PET) scan showed a positive sign corresponding to the nodule[ standardized uptake value (SUV) max 5.8]. No diagnostic material was obtained from the transbronchial tumor biopsy, since it was difficult to rule out malignancy, surgical biopsy was performed with sampling of mediastinal lymph nodes. Histopathological examination showed marked infiltration of inflammatory cells, many of which were demonstrated to be immunoglobulin (Ig) G4-positive plasma cells by immunohistochemical staining. Hence, IgG4-related inflammatory pseudotumor of the lung was diagnosed.