CEACAM5 and neoplasm: In multivariable analysis of the training cohort (Table 3), occult N2 lymph nodes metastases were significantly correlated with sex (P = 0.031), age (P = 0.001), history of cancers (P = 0.041), family history of cancers (P = 0.047), history of other lung diseases (P = 0.037), smoking history (P = 0.042), clinical stage (P = 0.045), clinical T stage (P = 0.033), clinical N stage (P = 0.029), tumor size (P = 0.037), tumor location (P = 0.026), central location (P = 0.034), and CEA (P = 0.007).