STANDARD TREATMENT FOR clinical submucosal invasive (cT1b) early gastric cancer (EGC) is surgery. Endoscopic submucosal dissection (ESD) can instead be carried out to predict the risk of lymph node metastasis when surgery is against a patient’s will or not feasible as a result of a patient’s age or comorbidities. However, ESD for cT1b EGC often results in a positive vertical margin. Herein, we developed endoscopic selective muscular dissection (ESMD), a new treatment method, to secure the vertical margin. An 80-year-old man presented with a lesion in the posterior wall of the stomach. The lesion had remarkable redness and an uneven surface (Fig. 1). He was diagnosed with cT1b EGC, but strongly refused to undergo surgery; thus, endoscopic resection was carried out. First, in the peripheral part where submucosal invasion was not suspected, circumferential mucosal incision and submucosal dissection were carried out, as done in conventional ESD. In the central part where submucosal invasion was suspected, we identified the oblique muscle layer and the circular muscle layer and then selectively dissected between these muscle layers with the assistance of dental floss clip traction. En bloc resection was achieved without perforation, retaining the circular muscle layer (Video S1). Histopathology showed that the adenocarcinoma invaded the submucosal layer just above the muscle layer, but was resected with negative vertical margin (Fig. 2). In the stomach, the muscularis propria consists of the inner oblique muscle, the middle circular muscle and the outer longitudinal muscle. Their distribution depends on the part of the stomach. Therefore, we should understand the distribution to avoid intraoperative perforation when carrying out ESMD. In addition, as the risk of delayed perforation

中文翻译：

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临床黏膜下浸润性早期胃癌的内镜选择性肌肉剥离术

临床黏膜下浸润性 (cT1b) 早期胃癌 (EGC) 的标准治疗是手术。当手术违背患者的意愿或由于患者的年龄或合并症而不可行时，可以进行内窥镜黏膜下剥离术 (ESD) 来预测淋巴结转移的风险。然而，cT1b EGC 的 ESD 通常会导致正的垂直裕度。在此，我们开发了内窥镜选择性肌肉剥离术 (ESMD)，一种新的治疗方法，以确保垂直边缘。一名 80 岁男性因胃后壁病变就诊。病变显着发红，表面不平整（图1）。他被诊断出患有 cT1b EGC，但强烈拒绝接受手术；因此，进行了内窥镜切除术。首先，在没有怀疑粘膜下浸润的周边部分，与常规 ESD 一样，进行了圆周粘膜切口和粘膜下层剥离。在怀疑黏膜下浸润的中央部分，我们确定了斜肌层和环形肌层，然后在牙线夹牵引的辅助下选择性地在这些肌层之间进行解剖。在没有穿孔的情况下实现了整块切除，保留了圆形肌肉层（视频 S1）。组织病理学显示，腺癌侵犯肌肉层正上方的黏膜下层，但切除后垂直切缘阴性（图 2）。在胃中，固有肌由内斜肌、中环肌和外纵肌组成。它们的分布取决于胃的部位。所以，进行ESMD时应了解其分布，避免术中穿孔。此外，由于延迟穿孔的风险