HDAC5 protein is expressed in lung, brain, myocardium, skeletal muscle, and placenta, and accumulating evidence indicates that it has variable expression and functions in different types of tumor: HDAC5 is overexpressed in breast cancer (19, 20), hepatocellular carcinoma (HCC) (21), lung cancer (22), pancreatic neuroendocrine cancer(pNET) (23) and colorectal cancer(CRC) (24). This evidence concerns the gene HDAC5 and primitive neuroectodermal tumor.