Figure 4.

Centriacinar emphysema caused by coal mine dust. Numerous (in the upper panels) and frequent (in the lower panels) birefringent silica/silicate particles with anthracotic pigment are present in the fibrotic thickened alveolar septa. There are only few birefringent particles in the rather normal lung tissue in the left lower corner of the upper panels and in the left part of the photomicrograph in the lower panels. On the left side are photomicrographs of H&E-stained tissue (original magnification 40× for the upper panels and 100× for the lower panels); on the right side are the same frames under polarized light.