The pathology of benign and malignant pleural disease.

A wide spectrum of diseases involve the pleura. Many of these occur as complications of other disease processes, such as infectious pneumonitis, although a pleural effusion or a pleuritis also can be the primary manifestation of a disease. The most common primary neoplasm involving the pleura is a mesothelioma. It is of interest because of its causation by asbestos and because of its wide spectrum of histologic variability. Metastatic tumors also frequently involve the pleura but may not necessarily be biopsied. One type of metastatic neoplasm involving the pleura that may be extremely difficult to differentiate from an epithelial mesothelioma is a pseudomesotheliomatous carcinoma. In most instances, malignant neoplasms can be diagnosed accurately and distinguished from one another by ancillary techniques, such as immunohistochemistry and electron microscopy.