近年来大量肿瘤发病机制的研究表明,微卫星不稳定(microsatellite instability,MSI)是继癌基因启动和抑癌基因失活后又一重要的肿瘤发生机制[1]。微卫星(microsatellite,MS)是短串核苷酸的简单重复序列,重复单位为2～6个核苷酸,重复次数在2O～100左右,广泛分布于人类基因组内。MS分为 In recent years, studies on the pathogenesis of a large number of tumors have shown that microsatellite instability (MSI) is another important tumor mechanism following oncogene activation and tumor suppressor gene inactivation [1]. Microsatellite (MS) is a simple sequence of short nucleotides with a repeat unit of 2 to 6 nucleotides and a repeat number of 2O to 100, which is widely distributed in the human genome. MS is divided into