Digital quantitative analysis of muscularis mucosae thickness in early gastric cancer specimens reveals anatomical variation.

The muscularis mucosae (MM) is a thin layer of smooth muscle in the gastrointestinal tract that may act as a barrier against carcinoma invasion; however, its characteristics in gastric cancer remain unclear. This study aimed to precisely measure MM thickness in early gastric cancer and assess its association with anatomical location, mucosal atrophy, Helicobacter pylori (H. pylori) infection status and cancer invasion. We analyzed 62 cases of early gastric cancer treated by endoscopic submucosal dissection (ESD), including 38 mucosa-confined (pT1a) and 24 submucosal-invasive (pT1b) cancers. The MM was visualized using desmin immunohistochemistry, and whole-slide imaging combined with digital image analysis enabled accurate quantification of MM thickness. The relationships between MM thickness and depth of invasion, tumor size, clinical parameters, anatomical location, mucosal atrophy and H. pylori infection were evaluated. No significant association was observed between MM thickness and cancer invasion, tumor size, or other clinical parameters. MM thickness was significantly greater in the pyloric antrum than in the gastric body and was thicker in the lesser curvature than in the greater curvature. In addition, MM thickness was significantly greater in cases with mucosal atrophy than in those without. Given the association between the presence of mucosal atrophy and increased MM thickness, together with the fact that the observed anatomical differences correspond to the distribution and progression of chronic gastritis, it is reasonable to speculate that chronic gastritis contributes to thickening of the MM.