[Pathological study of the natural history of pulmonary infarction mainly seen in lung tumors--pulmonary infarction begins with alveolar wall bleeding].

This study investigated the histological features of pulmonary infarction (PI). We examined lung tissue samples from 25 patients with PI treated in our hospital. The mean patient age was 59 years, 21 were men, and 4 were women. In 22 cases, the PI was located at the periphery of lung cancers. The mean number of slides examined was 2.7 including ordinary and immunohistochemical examinations. There were 3.6 PI per case. Eight cases of alveolar wall bleeding suspected of being at the beginning stage of infarction were characterized by partial alveolar epithelial and capillary endothelial disruption from the alveolar wall and separation of epithelial and endothelial basement membranes (BM). Eleven cases showed acute PI characterized by marked dilatation of the alveolar wall and separation of epithelial and endothelial BM in necrosis. Fourteen were organizing PI. Seven were organized PI with fibrotic encapsulation and partial organization of the infarction. The beginning stage of pulmonary infarction shows separation between epithelial and endothelial BMs and bleeding into the alveolar wall. The organized stage of PI shows gradual organization of infarction.