We hypothesized that if SCLCs or LCNECs harbor targetable mutations, then they stem from alveolar type II cells and are accompanied by adenocarcinoma-like features (i.e., are genetically similar to adenocarcinoma, histologically including an adenocarcinoma component, or positive for TTF-1 by immunohistochemistry). Here, TTF1 is linked to adenocarcinoma.