Fig. 2

Histopathological findings of the lung nodules. a Macroscopic examination of a white hard nodule in the right middle lobe. b Low-magnification image of a hematoxylin and eosin (HE) stained specimen revealed granuloma formation with foreign body-type giant cells (arrow) and mild and focal chronic inflammatory changes with eosin-positive deposits (asterisk). c and d The images of direct fast scarlet (DFS) staining revealed that the deposits were DFS positive (asterisk) (c, at lower-magnification, and d, at higher-magnification). e The DFS staining-positive lesions produced an apple-green birefringence under crossed polarized light (arrows) (× 100). The collagen fibrils appeared white (arrow heads). f The deposits were Congo red positive (asterisk). Foreign body-type giant cells were detected (arrows) (× 100). g and h A representative photograph of HE stained specimen (g) and its image of electron probe X-ray microanalysis (EPMA) (h). A two-dimension EPMA-wavelength dispersive spectrometer (WDS) image of an elemental map corresponding to the area shown in (h), showing orange dots indicating silica (Si) accumulated in giant cells (arrows). The distribution of amino nitrogen was colored green (h)