Pleuritis and Pleural Plaque
Pleuritis is a reactive process that may or may not include inflammatory cell infiltrates. In the typical frozen section, the pathologist may see fibrinous exudates on the pleural surface (fibrinous pleuritis), organization of the fibrin by granulation tissue (organizing pleuritis), or maturing or mature connective tissue (fibrous pleuritis). Causes of fibrinous and fibrous pleuritis are listed in Table 4.1. In combination with any of these findings, or as a dominant finding, the pathologist may see lymphocytes, lymphoid aggregates and plasma cells (chronic pleuritis - see Table 4.1), eosinophils (eosinophilic pleuritis - see Table 4.2), or granulomas (granulomatous pleuritis - see Table 4.3). Eosinophilic pleuritis is often the result of air and/or blood in the pleura from any etiology and is commonly seen in specimens from patients with pneumothorax and/or hemothorax with a wide range of causes. Bacterial infections may produce empyema with neutrophils and leukocytoclastic necrosis with basophilic debris (Figs. 4.1-4.4).