Analysis of individual biomarkers revealed that CEA and CYFRA 21-1 also distinguished adenocarcinoma (CEA: AUC = 0.665, p = 0.0004; CYFRA 21-1: AUC = 0.629, p = 0.0033) and squamous cell histologies (CEA: AUC = 0.649, p = 0.0180; CYFRA 21-1: AUC = 0.643, p = 0.0484) as shown in Additional file 1: Table S5. Here, CEACAM5 is linked to adenocarcinoma.