Asbestosis has a pattern of UIP with peripheral honeycombing and asbestos bodies.

Asbestos bodies

An iron-protein coat is applied to inhaled asbestos fibers within a macrophage. The resulting beaded or cylindrical ferruginous bodies are assumed to have an asbestos core if a transparent, uncoated portion can be seen or if the person has a history of asbestos exposure. Other types of mineral fibers can become ferruginous bodies.

Multiple, blue, beaded and cylindrical asbestos bodies can be seen in this iron-stained section. Asbestos bodies appear brown in H&E-stained sections.

Pleural plaque

Pleural plaques are sharply demarcated patches with a smooth or bumpy, pearly white surface. They occur on the parietal and diaphragmatic pleural surfaces and are usually associated with asbestos exposure. The three plaques shown here are on the diaphragmatic surface. Adhesions to the lung do not occur.

Non-specific, fibrous pleural plaque

These plaques are composed of dense, sparsely cellular fibrous tissue. The deep surface (left) usually has some lymphoid aggregates. The pleural surface (right) may show some fibrinous exudate. Dystrophic calcification often occurs in the plaque.

Pleural plaques are not believed to predispose to cancer. Asbestos fibers, but not asbestos bodies, have been found in them.

Rounded atelectasis

Note the focal thickening of the visceral pleura, which differs from the pleural plaque in location. Pleural infolding (between arrows) and alveolar atelectasis, which may be associated with visceral pleural thickening, sometimes produce an opacity resembling tumor on radiographs.