Bronchogenic squamous cell carcinomas with invasion along alveolar walls

In bronchogenic squamous cell carcinoma, a growth pattern along the alveolar walls of the peripheral lung parenchyma is unusual. In order better to understand the way tumour cells invade the peripheral lung parenchyma, we studied two cases of squamous cell carcinoma with invasion along the alveolar walls (in 30% to 40% of the area surrounding the tumour). We used immunohistochemical staining with antibodies against pulmonary surfactant, apoproteins (PE-10) and collagen type IV, and electron microscopy. Tumour cells invading the peripheral lung tissue were located between one layer of type II alveolar epithelial cells and the basement membrane of the alveolar walls. These results suggest that the cells of a squamous carcinoma (unlike an adenocarcinoma) have the ability to spread along the basement membrane of the alveolar walls without destroying pre-existing normal peripheral lung parenchyma.