Pneumoconiosis - Silicosis
Silicosis is a pneumoconiosis produced by chronic exposure to silica dust (workers in glass industry, sand blasters, miners, grinders and polishers, cement workers). After inhalation, silica particles are phagocytated by macrophages which shortly after die and so, the released silica particles will be phagocytated by other macrophages. These macrophages seems to secrete a fibroblast grown factor which stimulates the fibrosis.
Pulmonary silicosis. Continuous accumulation of collagen around inhaled silica crystals produces pulmonary fibrotic hyalinized (silicotic) nodules. They present concentric laminated collagen fibers (blue) and tend to become confluent, compressing adjacent alveoli. Silica crystals appear as empty cleft-like spaces. With progression, perivascular and peribronchiolar collagen deposits will produce pulmonary hypertension. (Simionescu trichromic staining, ob. x4)