The esophageal wall is histologically divided into four layers: the mucosa, the submucosa, the muscularis and the adventitia. The upper section of the esophageal muscularis propria is composed of skeletal muscle,the lower is smooth muscle, and the middle is a mixture of both. The esophageal muscularis propria is subdivided into an inner circular and an outer longitudinal layer in terms of the orientation of its muscle fibers. Thickening of the circular layer of the muscularis propria at the upper and lower end of the esophagus formed the upper esophageal sphincter (UES) and lower esophageal sphincter (LES) respectively. The esophageal adventitia is a fibrosa.

The gastrointestinal SMTs from muscularis propria mainly include leiomyoma, leiomyosarcoma and stromal tumors (GISTs), more common with leiomyoma and stromal tumors. Leiomyoma and leiomyosarcoma are mostly benign and originate from the smooth muscle, while stromal tumors originate from the interstitial cell of cajal in the gastrointestinal tract [1].

The esophageal SMTs from muscularis propria mainly includes leiomyoma, stromal tumors and leiomyosarcoma. The leiomyoma and stromal tumors are more common and their incidence ratio is 3:1.

The esophageal leiomyoma is derived from the esophageal smooth muscle, showing a predilection for the middle-lower esophagus and is prevalent more in men than women at the age of 20–60. The esophageal leiomyomas are round, oval or irregular in shape, with a smooth surface, hard texture, and a capsule. They usually grow localized within the esophageal wall protruding to the esophageal lumen, a few to the mediastinum. The tumors grow slowly, so the patients often have no early symptoms. With the growth of the tumor, esophageal luminal stenosis may appear to induce dysphasia, which is usually mild and slow to progress. Chest pain, palpitation, chest tightness etc. would present in patients carrying huge tumors.

The esophageal stromal tumor is rare, of which the majority has a soft texture. Most GISTs show one of three histologic patterns: spindle cell type, epithelioid cell type, or a mixture of both spindle and epithelioid cells. Epithelioid GISTs may have either a diffuse or nested architecture, whereas spindle cells GISTs are arranged in short fascicles or whorls. The morphology of the spindle cell type is relatively uniform. Most of the tumors lack a capsule. Patients with larger tumor may have secondary hemorrhage and necrosis. Most esophageal stromal tumors are benign, with potential malignance.

Early stage of esophageal SMTs from muscularis propria is generally asymptomatic. The most common clinical symptom in later stage of the disease could be dysphagia which is mostly mild and intermittent or slowly progressive. The degree of dysphagia is associated with how much of the esophageal lumen has been surrounded by the tumor.

The other symptoms include retrosternal pain, burning sensation or discomfort, abdominal pain or discomfort, palpitation, chest tightness, and weight loss. With the growth of tumor, symptoms such as hematemesis and melena may also occur.

A large proportion of the esophageal SMTs from muscularis propria are detected incidentally during endoscopy, which is an important means for their diagnosis. It may be seen endoscopically that a round or oval submucosal masse protrudes into the esophagus lumen with a smooth mucosal cover (Fig. 8.1a), and slides up and down underlying the mucosal layer during esophageal peristalsis. Esophageal tumors can cause eccentric stenosis, but the esophageal wall is not rigid, and the endoscope can get through. It is difficult to obtain the deep tissue for diagnosis by conventional biopsy, but biopsy forceps touching can show mucosal slipping motion which can be used to distinguish the SMTs from the mucosal tumor. EUS can define the growth pattern of tumor, either intraluminal or extraluminal, and judge its nature. Homogeneous hypoechoic lesion mixed with a small amount of strong echo in the fourth layer (muscularis propria) (Fig. 8.1b) can be showed by EUS which can make a distinction between the SMTs from muscularis propria and esophageal mucosal tumors as well as the compression from outside of the esophagus. Barium contrast radiography has a certain value in the diagnosis of esophageal SMTs from muscularis propria, which expresses as the semicircular cup-shaped sign being perpendicular to the long axis of the esophagus. CT and MRI help to evaluate whether mediastinal development happens, and to determine the suitability of endoscopic resection. Compared with the conventional endoscopy, EUS-guided fine needle aspiration biopsy significantly improves the positive rate of diagnosis of esophageal stromal tumors. Positive immunohistochemical CD117 staining is the key to the diagnosis of GISTs.

Indication: The diameter of the SMTs is less than 2.5 cm.

Relative indication: the diameter of the SMTs is 2.5–3.5 cm.

Relative contraindications: SMTs that do not have room for the tunnel or adhesions between tumor and epithelium cannot be separated, or the diameter of tumors is more than 3.5 cm, and the tumor cannot be taken out from the tunnel completely.

Absolute contraindications: Endoscopic resection cannot be performed because of severe cardiopulmonary dysfunction; coagulopathy; tunneling site with a large area of scar or anastomosis; ulceration on the surface of the SMTs.

It is best to use the endoscope with an auxiliary water channel (GIF-260J) and to select a electric knife on the preferences of the operators (detailed in Chap.​ 11). Hemostasis by hot biopsy forceps is often required during the procedure.