pointed out that the respiratory epithelium in mouse with only oncogenic Kras G12D cannot induce mucinous adenocarcinoma; only when Nkx2‐1 expression is reduced (haploinsufficiency) and Kras^G12D is present can lesions resembling human mucinous adenocarcinoma form. The gene discussed is NKX2-1; the disease is mucinous adenocarcinoma.