Fig. 1. Definition of detection of gastric cancer and determination of the horizontal extent of gastric cancer. (A) Type 0-IIc early gastric cancer is shown on the bottom left of the endoscopic image (yellow arrows). (B) Endoscopic images were divided into 9 sections using lines that divided the length and width into 3 equal parts. The lesion is present in sections 4 and 7. Detection of gastric cancer was defined as correct when any of the sections that included gastric cancer (either section 4 or 7 in this image) were identified. Determination of the horizontal extent of gastric cancer was defined as correct when all the sections that included gastric cancer (both sections 4 and 7 in this image) were identified. (C) When endoscopists selected section 4, the detection of gastric cancer was correct, but the determination of the horizontal extent of gastric cancer was incorrect. (D) When endoscopists selected both sections 4 and 7, both detection of gastric cancer and determination of the horizontal extent of gastric cancer were correct.