Fig. 3
a Chest computed tomography scan in a 55-year-old man shows a spiculated mass in the right middle lobe. b Histopathological specimen obtained from this patient shows distorted alveolar structures and thickened pleura. c Diffuse lymphoplasmocytic infiltrates and fibrosis are observed at high magnification (H&E; ×100). d An increased IgG4+ cell count is identified (IgG4 immunostaining; ×100)