As was the case with peripheral blood, LunX mRNA was the most specific marker in malignant pleural fluid, showing a high positive detection rate in lung cancer (13 of 14, 92.9%), compared with the other gene markers CK19, CEA, VEGF-C and hnRNP A2/B1 mRNA (Figure 4, Table 6). Here, CEACAM5 is linked to lung cancer.