CEACAM5 and adenocarcinoma: Tsai et al. [31] found in their retrospective study that abnormal serum levels of carcinoembryonic antigen, solid tumor diameter ≥ 1.3 cm, and consolidation to tumor ratio ≥ 0.50 on chest CT were predictive factors for lymph node upstaging in patients with clinical T1a-bN0M0 adenocarcinoma undergoing lobectomy and systematic lymphadenectomy, suggesting that if none of these predictive factors is positive, a less invasive procedure with lymph node sampling or no lymphadenectomy may be a reasonable alternative.