CHI3L1 and esophageal squamous cell carcinoma: The serum levels of YKL-40 in patients with ESCC were significantly higher than those of healthy control subjects (p < 0.001) and those of patients with benign disease (p = 0.038), and the serum levels of YKL-40 of the early-stage ESCC patients were significantly higher than healthy control subjects (p < 0.001) but similar to benign disease patients (p = 0.2126) (Figure 2).