Fig. 4

Histopathological findings of the pulmonary tissue (light microscopy: HE). a Pulmonary tissue shows fibrotic changes of the interstitium (× 100) in the lung. b Cell and tissue reactions and cellulosic exudation were observed in alveoli (× 200). c, d Giant cell, interstitial edema, collagen fiber hyperplasia and masson body were observed in the specimen (× 200). e, f Immunohistological analysis revealed CD38-positive plasmacyte (coloured brown) (E × 400) and CD138-positive plasmacyte (coloured brown) infiltration (F × 400). g IgG immunostaining shows IgG-positive plasmacyte (coloured brown) infiltration (× 400). h IgG4 immunostaining shows IgG4-positive plasmacyte (coloured brown) infiltration in the lung (× 400)