Some patients undergo gastroscopy because of dysphagia or gastric disorders, and as a result, a submucosal mass (SMT) in the esophagus is found, and the physician recommends ultrasound endoscopy to determine whether it should be removed endoscopically or surgically. A submucosal mass is a mass-like lesion caused by a tumor or other inflammatory or anatomical abnormality originating in the submucosal tissue of the esophagus. The normal esophagus has four layers, which should be like the walls of a house. The innermost layer against the lumen of the esophagus is the mucosal layer, which is like the stucco layer of the wall, and the masses occurring there can usually be removed endoscopically. The middlemost layer is the intrinsic muscular layer, which is like the brick layer of the house, and this layer is the support of the digestive tube. Between the mucosal layer and the intrinsic muscular layer is the submucosal layer, which is like the gap between the stucco layer and the bricks. What is the best way to know if a mass in the esophagus occurs in the submucosa and not in the intrinsic muscular layer, i.e. which mucosal masses are found by endoscopy that can be removed by simple endoscopy without surgical intervention? The best way is to do an ultrasound endoscopy (EUS), because gastroscopy can only look at the surface of the mass, and if ultrasound is mounted on the gastroscope head, it is possible to see the inside of the mass as well as the ultrasound, so that it is clear whether the mass occurs in the submucosa or in the intrinsic muscular layer. Most submucosal masses are of mesenchymal origin and commonly include smooth muscle tumors, hemangiomas, lipomas, granulocytic or myoblastomas. A small number can also come from epithelial tissue, such as submucosal cysts. SMT is mostly benign, but some can be malignant, such as malignant mesenchymal tumors. The nature of the lesion can be determined by pathological examination through endoscopic excision. In some cases, if the size of the lesion is small and the patient does not want to undergo surgery, the lesion can be ligated by endoscopic means and left to die naturally, which is a simple and safe treatment.