Objective To explore the relationship between microsatellite instability （MSI） and gastric cancer. Methods The related literatures at home and abroad were consulted and reviewed. Results The MSI is the replication errors caused by mismatch repair system defects. Gastric cancer which exhibiting MSI has characteris clinicopathological feature and prognosis. Detection the MSI of precancerous lesions and gastric cancer tissues can evaluate the risk and prognosis of gastric cancer. MSI include nuclear microsatellite stability （nMSI） and mitochondrial microsatellite instability （mtMSI）. Conclusions MSI plays an important role in the occurrence and development of gastric cancer. MSI may become a important indicator to forecast precancerosis risks and clinical prognosis of gastric cancer.
A microsatellite is a short, repetitive sequence of DNA (usually 2 to 4 nucleotides in length). Multiple primary lung cancers (MPLC) are more than one primary lung cancer lesions arising synchronously in different locations of the same or different side of the lung. These neoplasms may have same or different histological types, but one lesion is not a metastasis from another, as each neoplasm arises independently in the lung. Abnormal microsatellite changes are closely related to the pathogenesis and development of MPLC. In this review, several aspects are discussed:①definition and origin of microsatellite; ②abnormal changes of microsatellite; ③definition and categories of MPLC; ④the influence of microsatellite on early diagnosis, treatment and prognosis of MPLC.