That a large fraction of our TTF-1 positive gastric, pancreatic, and colorectal carcinomas was indeed positive for at least one of the markers CK20, Villin-1, SATB2, and FABP1 is supportive of this concept, but expression of at least one of these markers also occurred in 22% of our TTF-1 positive pulmonary adenocarcinomas. This evidence concerns the gene KRT20 and colorectal carcinoma.