Chitinase 3-like protein 1 (CHI3L1), also known as YKL-40 in humans, is a secreted glycoprotein with multiple functions that is expressed in various cell types, including endothelial cells, activated macrophages, chondrocytes, neutrophils, fibroblasts, synovial and various tumor cells6. The gene discussed is CHI3L1; the disease is neoplasm.