By polarized light microscopy one can visualize the etiology for most pneumoconioses (even those in many coal miners)--silica crystals. Here are seen bright white crystals of varying sizes. The silica induces a fibrogenic response when macrophages ingest the crystals and secrete cytokines to induce a predominantly fibrogenic response. The result is the production of many scattered nodular foci of collagen deposition in the lung.

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