Although it has been suggested that YKL-40 is expressed and secreted by macrophages, neutrophils, fibroblast-like synovial cells, chondrocytes, vascular smooth muscle cells and hepatic stellate cells [22], which may partly explain the elevation of serum YKL-40 in HCC patients, the exact mechanisms responsible for this abnormal secretion should be examined in vitro or in vivo in future study. This evidence concerns the gene CHI3L1 and hepatocellular carcinoma.