Study Syllabus for Classification of Radiographs of Pneumoconioses

Pathology Overview

Pathology Basis of Occupational Lung Disease

Pulmonary Silicosis

Mixed-Dust Fibrosis

In some industrial settings, such as foundry work or coal mining, the inhalation of free crystalline silica in conjunction with other minerals leads to a characteristic stellate nodule of mixed-dust fibrosis. The stellate nodule, as opposed to the more classical rounded silicotic nodule, has irregular extensions into the adjacent lung parenchyma, producing a “Medusa-head” lesion (Fig. 21). Abundant black pigment and brightly birefringent silicate particles impregnate stellate nodules. Since a mixture of nonsiliceous minerals and/or black pigment is often seen in association with classical silicosis, the determinants for the development of mixed-dust fibrotic nodules are somewhat uncertain [Silicosis and Silicate Disease Committee 1988].

Acute and Accelerated Silicosis

Acute silicosis is characterized pathologically by the filling of alveolar spaces by lipoproteinaceous material that stains red-violet with periodic acid–Schiff stain (Fig. 22). There may be associated diffuse alveolar septal fibrosis and small, cellular, poorly formed silicotic nodules [Silicosis and Silicate Disease Committee 1988; Buechner and Ansari 1969]. In acute silicosis, silica particles may be difficult to visualize with polarized light because of their exceedingly small size. Accelerated silicosis is also a severe progressive form of silicosis caused by inhalation of abundant fine silica particles. The time course of accelerated silicosis is intermediate in duration between acute and chronic silicosis. Cellular silicotic nodules may resemble granulomas in the early stages, with progression to massive conglomerate fibrosis in the later stages of the disease.