In the study, positive expression of CK20 and CK7 in tumor tissues and non-carcinoma adjacent tissues of lung cancer might be related to the functional enhancement of intermediate filament synthesis in the cells of these abnormal hyperplastic epithelial tissues, suggesting that the positive expressions of CK7 and CK20 might correlate strongly with the formation of lung cancer and the progression of such cancer. This evidence concerns the gene KRT20 and cancer.