THE HETEROGENEITY OF MICROSATELLITE INSTABILITY IN MULTIPLE GASTRIC CANCERS

To obtain a better understanding of the role of genetic instability in developing gastric cancer, it is of great interest to examine microsa tellite alterations in synchronous multiple gastric cancers that are t hought may have the same genetic background and the same microenvironm ent of the stomach. We report our experience with two patients with sy nchronous multiple gastric cancers: patient 1 showed two carcinomas in the stomach, whereas patient 2 showed two carcinomas and two adenomas in the stomach. We examined the DNAs from the two cases for microsate llite instability and expected that the status of microsatellite insta bility in each tumor from the same stomach would be the same. However, patient 2 revealed heterogeneity in the microsatellite instability, i .e., an early cancer that showed some apparent alterations, whereas th e other advanced cancer and two adenomas did not. On the other hand, n either of the two carcinomas in patient 1 showed microsatellite instab ility. To our knowledge, there has been no previous report of microsat ellite instability in multiple gastric cancers. In this report, we des cribe a case that revealed such a heterogeneity of the microsatellite instability, in which the carcinogenic process of each tumor may under go different genetic alterations even under the same genetic condition s and background.