Role of arterial occlusion in pulmonary scar cancers.

The pathogenesis of scars in lung carcinomas was studied in 57 consecutively resected small (less than or equal to 3 cm) peripheral lung cancers. Central, pigmented scars rich in elastic fibers were most frequently found in adenocarcinomas with predominantly non-destructive, intraalveolar growth pattern. In these cancers with elastin-rich scars, active neoplastic occlusion of one or more arteries was almost always found (96%). Infarction of tumor tissue and its supporting pulmonary stroma was frequently seen separating the central scar from the viable peripheral tumor zone. The elastic fibers of alveolar walls survived and condensed into a compact central scar. Based on these observations, it is suggested that scarring in peripheral lung cancers is often caused by mechanisms unique to the lung. Lung cancers often invade and occlude branches of pulmonary arteries, causing ischaemic necrosis (infarction) of the neoplasm and its stroma. In these neoplasms, often growing mainly in air spaces and preserving the pulmonary framework as their stroma, the elastic fibers of the aLveoli remain preserved despite necrosis, so that the alveolar elastic collapses to form the characteristic elastin-rich scar following absorption of necrotic debris.