CK7 has a high sensitivity and is expressed in almost 100% of lung adenocarcinoma, but its specificity is poor and it is also expressed in 30–70% of lung squamous cell carcinoma, and P40 is basically not expressed in lung adenocarcinoma, but is expressed in more than 96.8% of squamous cell carcinoma. The gene discussed is KRT7; the disease is squamous cell carcinoma.