Correlation between microsatellite instability-high phenotype and occult lymph node metastasis in gastric carcinoma

The aim of this study is to investigate the association of microsatellite instability (MSI) status with nodal status in gastric carcinoma (GC). MSI status was investigated in 623 consecutively resected GCs. To detect occult lymph node (LN) metastasis, immunohistochemistry (IHC) using antibodies against pan-cytokeratin was performed in 391 node-negative cases by initial histologic examination. MSI-high (MSI-H) phenotype was found in 68 GC cases (10.9%) and was significantly associated with increased patient age, antral location, intestinal type, absence of venous/perineural invasion, and expanding growth type (p < 0.05). When the nodal status was evaluated, the number of metastatic LNs of MSI-H tumors tended to be lower than that of microsatellite stable/MSI-low (MSS/L) tumors (1.49 ± 3.15 vs 4.37 ± 9.81; p = 0.052), but the MSI-H phenotype was associated with the presence of lymphatic invasion (p = 0.036) and IHC-positive occult LN metastasis (p = 0.007). By multivariate analysis, MSI-H phenotype was significantly associated with IHC-positive occult LN metastasis (Odds ratio, 2.654; p = 0.044). MSI status and occult LN metastasis were not prognostic factors by survival analysis. Our findings suggest that the relationship between MSI status and regional LN metastasis may have some clinical and biologic implications to be elucidated.