Microsatellite instability in Japanese gastric cancer

Recent studies have shown that microsatellites are unstable in various types of cancers, and such genetic instability at the microsatellite loci (microsatellite instability) has been considered to play an important role in the development of cancer. However, the clinicopathologic significance of microsatellite instability in gastric cancer has not been clarified.

To elucidate the role of genetic instability in the development of gastric cancer, the presence of microsatellite instability was examined in 25 cases of gastric cancer using fresh-frozen tumor-normal paired samples using a polymerase chain reaction (PCR)-based method. Microsatellite instability was defined as tumors that showed altered banding patterns at two or more microsatellite loci.

The incidence of microsatellite instability in gastric cancer cases was 4 of 25 patients (16%) and 4 of 26 cancers (15%). A significantly high incidence of microsatellite instability was observed in both the elderly (P < 0.01) and in lymph node metastasis-negative patients (P < 0.05). All patients with gastric cancer showing microsatellite instability were negative for lymphatic or venous permeation. A statistically significant association of microsatellite instability with no lymphatic permeation was thus observed (P < 0.05).

This study revealed infrequent lymph node metastasis and lymph vessel invasion in the patients with gastric cancer demonstrating microsatellite instability. Although the number of examined cases was small, these findings suggest that gastric cancer that shows microsatellite instability may thus behave in a less malignant manner.