Stretching Causes Extensive Changes of Gastric Submucosa: Is It Acceptable to Define 500 microm as the Safe Margin?

Background/aims: Endoscopic mucosal resection can cure early gastric cancer. The risk of lymphatic metastasis is related to the depth of submucosal invasion by the mucosal malignancy, with a resection depth of 500 microm generally accepted as a safe cut-off. However, excessive thinning induced by stretching of the resected tissue sometimes preventing a precise diagnosis. We studied the effects of stretching on different layers and sites of gastric tissue.

Methods: Porcine stomachs were cut into 2.0x2.0 cm pieces, and pieces from body were stretched to 2.5, 3.0, and 3.5 cm. Pieces from the cardia, body, and antrum were also stretched to 3.0 cm. The thickness of each layer was measured and analyzed statistically.

Results: Whole gastric wall and submucosal layers showed gradual thinning, with stretching to 3.5 cm tearing the tissues and resulting in imperfect extension. The submucosa was thinner in body tissue than in cardia and antrum tissues. Stretching to 3.0 cm induced a consistent decrease in submucosal thickness (30-70%). The change in thickness varied widely between individual samples.

Conclusions: A resection margin of 500 microm might be insufficient for the complete removal of malignancy. Moreover, the thickness of the submucosal layer differs with the gastric site and between individuals. Future studies are needed to confirm the findings in human tissue.