Microsatellite instability in multiple gastric cancers.

To better elucidate the role of genetic instability in the development of gastric cancer, microsatellite alterations were examined in a total of 30 gastric cancers that developed in 14 Japanese patients with multiple gastric cancers, which are considered to have possibly occurred under the same genetic background and in the same microenvironment of the stomach. Microsatellite instability (MSI) in multiple gastric cancers was recognized in 11 out of 14 cases (78.5%) and in 16 out of 30 cancers (53.3%). Eight out of 11 cases showing MSI exhibited a heterogeneity of microsatellite alterations. The incidence of microsatellite instability in the multiple gastric cancers cases was significantly higher than that in the solitary gastric cancer cases reported previously (20.8%: 5 out of 24 cases). These results suggested that (1) genetic instability plays a more important role in the development of multiple gastric cancers than in that of solitary gastric cancer and (2) the heterogeneity of MSI in multiple gastric cancers may not be a rare event, although the significance of the heterogeneity could not be clarified.