Among the different histological types of lung cancer, patients with non-small cell lung cancer (NSCLC), which is composed of adenocarcinoma and squamous cell carcinoma, had a higher CK19-2G2 level than patients with SCLC (9.20±10.27 vs. 6.46±6.23 mU/mL, P = 0.023) (Table 2). Here, KRT19 is linked to adenocarcinoma.