A proposed five-gene diagnostic signature, including KRT5, MUC1, TREM1, C3, and TMPRSS2 [40], as well as an eight-gene classifier for lung cancer subtypes [41], exhibited a high predictive accuracy of 0.936 during testing on 2556 adenocarcinoma samples and 1630 squamous cell carcinoma samples. Here, TMPRSS2 is linked to adenocarcinoma.