Microscopic Invasion Patterns and Epithelial Cell-phenotypes in Early Gastric Cancer with Submucosal Invasion

Background and study aims: Early gastric cancers show gastric and/or intestinal phenotypes with specific mucin production profiles, and the phenotypes can vary with tumor progression. The aim of this study was to evaluate the correlation between tumor invasion patterns and phenotypes in the mucosa and submucosa of early gastric cancers. Methods: Phenotypic expressions of 44 endoscopically resected gastric cancers with submucosal invasion were evaluated immunohistochemically using MUC5AC and MUC6 as gastric and MUC2 and CD10 as intestinal phenotypic markers. Results: Cancers were classified into two patterns by invasion pattern: 19 collapsing pattern (C-pattern) tumors had cancer cells that invaded to the submucosa with expansive destruction of the muscularis mucosae, while 25 passing-through pattern (P-pattern) tumors formed focal cancer cell aggregations in the submucosa without massive destruction of the muscularis mucosae. Cancers with C-pattern invasion were likely to show similar phenotypes between the mucosa and submucosa, while phenotypes of cancers with P-pattern invasion were likely to differ between the two layers (rate of the same phenotypes: C-pattern 68% vs. P-pattern 28%, p = 0.008). Of 22 cancers with P-pattern invasion that included the intestinal phenotype component in the mucosa, 13 (59%) expressed the gastric phenotype alone in the submucosa. Conclusions: Phenotype presentation in the mucosa and submucosa differ by the invasion pattern in early gastric cancer. Tumors with P-pattern invasion are likely to express the gastric phenotype in the submucosa, regardless of phenotype in the mucosa, suggesting that such cancers might achieve submucosal invasion prior to intestinalization occurring in the mucosa.