SFTPC and lung adenocarcinoma: Although the peripheral location and molecular phenotype of murine and human lung adenocarcinoma (i.e., the expression of the alveolar epithelial marker SFTPC) suggest an alveolar origin, we show here that both airway and alveolar cells are found in environmental-induced lung adenocarcinoma and that, in fact, airway cells may play a more prominent role during the initial steps of carcinogenesis.