CHI3L1 and esophageal squamous cell carcinoma: Figure 2 presents the serum levels of YKL-40 in the patients with ESCC (n = 150), patients with benign esophageal diseases (n = 59), healthy controls (n = 126) and patients with early-stage ESCC (n = 47, 7 cases of stage I, 40 cases of stage II).