Diagnostic performance of conventional endoscopy in the identification of submucosal invasion by early gastric cancer: the "non-extension sign" as a simple diagnostic marker.

Background and aim The ability to differentiate between mucosal (M) or microinvasive submucosal (SM1: depth of less than 500 µm) and invasive submucosal (SM2: depth of 500 µm or more) cancer is paramount when choosing the method of treatment for early gastric cancer (EGC). The “non-extension sign” relatesto a localized increase in thickness and rigidity due to massive submucosal invasion by a cancer. The present study sought to assess the ability of conventional endoscopy (CE) to correctly identify SM2 cancer using only the non-extension sign.