TTF1 and adenocarcinoma: In this context, the adenocarcinomas are characterized with expression of CK14, transcription factor Nkx2.1 (TTF1), CCSP, and SPC and arose from the BADJ in murine model, suggesting that club cells or AEC II cells stem/progenitor cells may be the initiating cells for adenocarcinomas in distal lung [3, 70, 71, 78, 81, 82].