The aim of this study was to investigate the relationship between microsatellite instability (MSI) and clinicopathologic features including multiplicity in early stage gastric neoplasias (ESGN).

From November 2004 until September 2009, 372 patients with consecutive resected gastric neoplasias were retrospectively enrolled. The gastric neoplasias were composed of 117 advanced gastric cancers (AGCs) and 255 ESGNs including 31 gastric dysplasias (including low and high grade dysplasia) and 224 early gastric cancers (EGCs).

Based on microsatellite markers, high MSI (MSI-H) was observed in 61 cases (16.4%) and low MSI (MSI-L) in 14 cases (3.8%) of 372 cases. There was a positive correlation between the presence of MSI-H and progression of gastric adenoma to gastric tumor. We compared ESGNs with microsatellite stable (MSS; 223 cases, 87.5%) and ESGNs with MSI-H (24 cases, 9.4%). The ESGNs with MSI-H were only associated with older age and female gender. There were no association with Helicobacter pylori infection, intestinal metaplasia, and distal location in contrast with EGCs with MSI-H. Furthermore, multiplicity of ESGNs was not associated with MSI status.

The clinicopatholgic features of MSI-H phenotype were different according to the progression of gastric neoplasias from ESGNs to AGCs. ESGNs with MSI-H were only associated with old age, female sex. In addition ESGNs with MSI-H were not associated with an increased risk of multifocal tumors.