CHI3L1 and small cell lung carcinoma: According to previously published studies, CHI3L1 expression increases in the serum and lungs of patients with idiopathic pulmonary fibrosis5, high serum CHI3L1 level in small-cell lung cancer patients is associated with early death6, and serum CHI3L1 levels in non-small-cell lung cancer and melanoma patients are used as independent pre-biomarkers7.