AIM: To investigate endoscopic and clinicopathologic characteristics of early gastric cancer (EGC) according to microsatellite instability phenotype. METHODS: Data were retrospectively collected from a single tertiary referral center. Of 981 EGC patients surgically treated between December 2003 and October 2007, 73 consecutive EGC patients with two or more microsatellite instability (MSI) mutation [high MSI (MSI-H)] and 146 consecutive EGC patients with one or no MSI mutation (non-MSI-H) were selected. The endoscopic and clinicopathologic features were compared between the MSI-H and non-MSI-H EGC groups. RESULTS: In terms of endoscopic characteristics, MSI-H EGCs more frequently presented with elevated pattern (OR 4.38, 95% CI: 2.40-8.01, P < 0.001), moderate-to-severe atrophy in the surrounding mucosa (OR 1.91, 95% CI: 1.05-3.47, P = 0.033), antral location (OR 3.99, 95% CI: 2.12-7.52, P < 0.001) and synchronous lesions, compared to non-MSI-H EGCs (OR 2.65, 95% CI: 1.16-6.07, P = 0.021). Other significant clinicopathologic characteristics of MSI-H EGC included predominance of female sex (OR 2.77, 95% CI: 1.53-4.99, P < 0.001), older age (> 70 years) (OR 3.30, 95% CI: 1.57-6.92, P = 0.002), better histologic differentiation (OR 2.35, 95% CI: 1.27-4.34, P = 0.007), intestinal type by Lauren classification (OR 2.34, 95% CI: 1.15-4.76, P = 0.019), absence of a signet ring cell component (OR 2.44, 95% CI: 1.02-5.86, P = 0.046), presence of mucinous component (OR 5.06, 95% CI: 1.27-20.17, P = 0.022), moderate-to-severe lymphoid stromal reaction (OR 3.95, 95% CI: 1.59-9.80, P = 0.003), and co-existing underlying adenoma (OR 2.66, 95% CI: 1.43-4.95, P = 0.002). CONCLUSION: MSI-H EGC is associated with unique endoscopic and clinicopathologic characteristics including frequent presentation in protruded type, co-existing underlying adenoma, and synchronous lesions.
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