CEACAM5 and neoplasm: In univariate analysis of the training cohort (Table 2), occult N2 lymph nodes metastases were significantly correlated with sex (P = 0.001), age (P < 0.001), height (P = 0.183), weight (P = 0.484), history of cancers (P = 0.031), family history of cancers (P = 0.009), history of other lung diseases (P = 0.003), smoking history (P = 0.023), clinical stage (P = 0.047), clinical T stage (P = 0.003), clinical N stage (P = 0.009), tumor size (P = 0.020), tumor location (P = 0.006), central location (P = 0.021), CEA (P = 0.006), and SCC (P = 0.593).