ROC analysis also demonstrated that the addition of YKL-40 to either tumor marker significantly increased the AUC of detection of ESCC (YKL-40 + CEA vs. CEA = 0.877 vs. 0.652; YKL-40 + CYFRA21-1 vs. CYFRA21-1 = 0.897 vs. 0.746; YKL-40 + SCCA vs. SCCA = 0.917 vs. 0.789). This evidence concerns the gene CHI3L1 and esophageal squamous cell carcinoma.