MICROSATELLITE INSTABILITY IN JAPANESE GASTRIC-CANCER

Background. Recent studies have shown that microsatellites are unstabl e in various types of cancers, and such genetic instability at the mic rosatellite loci (microsatellite instability) has been considered to p lay an important role in the development of cancer. However, the clini copathologic significance of microsatellite instability in gastric can cer has not been clarified. Methods. To elucidate the role of genetic instability in the development of gastric cancer, the presence of micr osatellite instability was examined in 25 cases of gastric cancer usin g fresh-frozen tumor-normal paired samples using a polymerase chain re action (PCR)-based method. Microsatellite instability was defined as t umors that showed altered banding patterns at two or more microsatelli te loci. Results. The incidence of microsatellite instability in gastr ic cancer cases was 4 of 25 patients (16%) and 4 of 26 cancers (15%). A significantly high incidence of microsatellite instability was obser ved in both the elderly (P < 0.01) and in lymph node metastasis-negati ve patients (P < 0.05). All patients with gastric cancer showing micro satellite instability were negative for lymphatic or venous permeation . A statistically significant association of microsatellite instabilit y with no lymphatic permeation was thus observed (P < 0.05). Conclusio ns. This study revealed infrequent lymph node metastasis and lymph ves sel invasion in the patients with gastric cancer demonstrating microsa tellite instability. Although the number of examined cases was small, these findings suggest that gastric cancer that shows microsatellite i nstability may thus behave in a less malignant manner.