However, at the bi- and multivariate analysis, factors associated with basal CEA serum levels ≥ 40 ng/mL were adenocarcinoma histological type (frequency of 41.3% compared with 14.1% of patients with squamous or large-cell histologies, RR 1.6; 95% CI, 1.4–3.4; p = 0.005) and presence of CNS metastasis at diagnosis (frequency of 77.7% compared with 12.3% of patients without CNS metastasis at diagnosis, RR 14.05; 95% CI, 5.7–34.4; p < 0.001). The gene discussed is CEACAM5; the disease is adenocarcinoma.