目的探讨微卫星不稳定性（ＭＳＩ）在多原发及单发大肠癌中的变化规律方法应用ＰＣＲ－ＳＳＣＰ技术对２４例多原发大肠癌和对照２１例单发大肠癌石蜡组织切片提取ＤＮＡ，并进行染色体不同位点微卫星不稳定性基因标志的检测结果多原发大肠癌中微卫星不稳定性的发生率为７１％（１７／２４），单发大肠癌微卫星不稳定性的发生率为３８％（８／２１），二者有明显差异（Ｘ２＝６．８２，Ｐ＜０．０２）ＭＳＩ阳性的多原发大肠癌主要发生在年轻的男性患者，与单发大肠癌相比（ｘ２＝４．６４，Ｐ＜０．０５），有统计学意义．多原发大肠癌ＭＳＩ阳性癌肿在右半结肠发生率及分布在ＤｕｋｅｓＡ，Ｂ期居多，但与单发大肠癌相比并无明显差异结论微卫星不稳定性在多原发大肠癌的发生发展中起重要作用，可作为预测大肠癌多原发倾向的有用标志 Objective To study the changes of microsatellite instability (MSI) in multiple primary and single colorectal cancers. Methods PCR-SSCP was used to extract DNA from paraffin tissue sections of 24 cases of multiple primary colorectal cancer and 21 cases of control single colorectal cancer. And the results of microsatellite instability gene markers detected at different loci of chromosomes The incidence of microsatellite instability in colorectal cancer was 71% (17/24). The microsatellite instability of single colorectal cancer The incidence was 38% (8/21), and there was a significant difference between them (X2=6.82, P<0.02). MSI-positive multi-primary colorectal cancer mainly occurs in young male patients, and single colorectal cancer Compared with (x2=4.64, P<0.05), there was statistical significance. The incidence and distribution of multiple primary colorectal cancer MSI-positive cancers in the right colon were mostly Dukes A and B, but there was no significant difference compared with the single colorectal cancer. Conclusion The microsatellite instability occurred in multiple primary colorectal cancers. Development plays an important role as a useful marker for predicting multiple primary colorectal cancer tendencies