Epithelial outgrowths from lung tissue following intrapleural injection of asbestos dust in experimental animals.

Abstract

AbstractAfter the intrapleural injection of asbestos dust in experimental animals, granulomas were produced and large areas of the pleural surface became thickened with fibrous tissue. In guinea‐pigs injected with chrysotile dust, alveolar epithelial cells often migrated through the lung surface and were found lining spaces in the areas of pleural fibrosis. Initially these cells exhibited the exact structure of the surfactin‐secreting type of alveolar cell, but later many of the cells lost the surfactin granules from their cytoplasm and became ciliated. In some animals cystic formation occurred in the lung tissue and groups of cysts grew out from the lung to invade the areas of pleural fibrosis. These cysts were also lined with surfactin‐secreting alveolar cells. The possible association of these epithelial outgrowths and the well‐known difficulties of diagnosing pleural mesotheliomas are discussed.