The incidence of gastrointestinal mesenchymal tumors is gradually increasing. However, the standardized guidelines and promotion of its treatment are lagging behind those of gastrointestinal cancer. For example, the first edition of the domestic CSCO guidelines for diagnosis and treatment was only released this year. Surgical treatment remains the most critical and potentially curative means of gastrointestinal mesenchymal tumor. The general principles of surgical treatment: to achieve R0 resection as much as possible, to ensure the principle of tumor-free, and to avoid tumor rupture. The timing of surgical treatment is not only related to the size of the tumor, but also closely related to the location of the tumor. Gastric mesenchymal tumor is the most common site of gastrointestinal tract and has relatively good prognosis. The traditional treatment concept is to consider surgical resection only when the gastric mesenchymal tumor is larger than 2 cm. However, it has been found that the biological behavior of mesenchymal tumors is related to clinical presentation and endoscopic manifestations, in addition to size. Therefore, the CSCO Guidelines for the Management of Gastrointestinal Mesenchymal Stromal Tumors 2020 edition has added recommendations for the treatment of small gastric mesenchymal tumors. The overall prognosis of small GIST is good, but a small proportion may still have adverse biological behavior, which includes both clinical manifestations and endoscopic manifestations. The clinical manifestations include tumor bleeding and ulcer formation; the endoscopic manifestations are adverse ultrasound gastroscopic signs, such as irregular borders, ulceration, strong echogenicity and heterogeneity. For patients with a primary site in the stomach and adverse factors, open surgical resection or laparoscopic resection is recommended for small GISTs exhibiting adverse biological behavior in class I, and laparoscopic or endoscopic resection (in an experienced laparoscopic center) is recommended for GISTs in the lesser curved side of the stomach, posterior gastric wall, and gastroesophageal union in class II (class 2B evidence). For patients with small GIST whose primary site is the stomach and without adverse factors, class I recommends regular follow-up observation (class 2A evidence), class II recommends open surgery for endoscopic follow-up difficulties, and laparoscopic resection for patients with suitable laparoscopic resection sites (class 2A evidence); for patients with GIST whose primary site is not the stomach, class I recommends open surgical resection or laparoscopic resection (class 2A evidence) . In the surgical treatment of gastrointestinal mesenchymal tumors, there are many points that need to be discussed and standardized. I. Scope of surgical resection Most gastrointestinal mesenchymal tumors grow in an expansile, mass-type manner, and most of them have an envelope. On CT, most of them appear as intracavitary or extracavitary masses with clear boundaries; a few of them may grow both inside and outside the cavity in a “dumbbell shape”; however, some of them appear as diffuse thickening of the gastric wall with unclear boundaries, which is highly similar to gastric cancer. Therefore, surgery for gastrointestinal mesenchymal tumors does not require enlarged resection, and it is usually sufficient to ensure negative margins. This can preserve the organ function to the maximum extent. This is especially true if the tumor grows in a critical area. For example, at the esophagogastric junction, rectum, esophagus, duodenum or pylorus of the stomach. Generally, the tumor can be removed 1cm or even 5mm from the root. The surgical resection method of gastrointestinal tract mesenchymal tumor is mainly open surgery or laparoscopic surgery. Laparoscopic surgery is relatively less traumatic, but there is a certain prerequisite for its application, that is, it cannot cause tumor rupture during the surgical operation. If the tumor is located in a special area, which makes laparoscopic operation difficult, it should be converted to open surgery in time, after all, the complete removal of the tumor is the first consideration. The common sites suitable for laparoscopic operation are: tumor located in the side of gastric greater curvature or anterior wall of gastric body, tumor located in the posterior wall of stomach or gastric fundus, but no obvious adhesion with the mass organ; small intestinal mesenchymal tumor with diameter less than 5cm and no adhesion with surrounding tissues, laparoscopic resection and digestive tract reconstruction can be considered, but for small intestinal mesenchymal tumor larger than 5cm, laparoscopic localization is recommended and direct open surgery is more reasonable. However, for small intestinal mesenchymal tumors larger than 5 cm, laparoscopic localization and direct open surgery are recommended, which can better protect the tumor and avoid medical rupture, and remove the specimen directly through the abdominal incision; for colonic mesenchymal tumors and medium to high rectal mesenchymal tumors, laparoscopic surgery can be chosen to remove them, similar to colon and rectal cancer surgery, but without clearing the lymph nodes like colorectal cancer surgery. What conditions are recommended to choose open surgery? For example, gastric mesenchymal tumor is located near the cardia, which is difficult to operate laparoscopically and may lead to cardia stenosis when closing the gastric wall, so open surgery is needed to cut the gastric wall under direct vision, excise the tumor according to its root and preserve the gastric wall to the maximum extent, and then close the wound manually to preserve the cardia function to the maximum extent. Hand suturing saves the gastric wall and reduces the risk of cardia stenosis than closing the opening with a cutting closure. The same is true for tumors located near the pylorus, which are excised under direct vision with open abdomen and hand sutured to avoid pyloric stenosis. For lateral wall tumor of duodenum, tumor diameter less than 2cm or exophytic tumor can choose open local excision and suture to avoid pancreatic head duodenal resection. 2.Tumor with large diameter or serious adhesion with surrounding organs There is no fixed standard for how many centimeters of tumor diameter are indications for choosing open surgery. Generally speaking, tumor diameter greater than 10cm is recommended to choose open surgery, even for exogenous tumor, because the large size of tumor affects the operation and increases the risk of tumor rupture due to intraoperative accidents; however, for endogenous mesenchymal tumor with diameter greater than 5cm, sometimes it is not suitable for laparoscopic surgery, because direct closure under laparoscopy will remove relatively more gastric wall and lead to narrowing of gastric lumen. Of course, size is not an absolute influencing factor. If laparoscopic surgery is performed skillfully and the tumor location is convenient for operation, it can still be done laparoscopically. For example, a tumor in the greater curvature or antrum of the stomach, even if endogenous, can still be easily done laparoscopically by incising the gastric wall along the base of the tumor and then suturing the wound (either by closing it with a linear cut closure or by hand). In addition, if the abdominal exploration reveals that the tumor is severely adherent to the surrounding organs, this situation is not suitable for laparoscopic surgery, as shown in Figure 2, because it increases the risk of tumor rupture during the process of separating the adhesions, and timely intermediate open surgery is recommended. Because the trauma of open surgery is negligible compared with the risk of recurrence caused by tumor rupture. 3.Tumor boundaries are not clear The vast majority of mesenchymal tumors have clear boundaries, but there are still a small number of mesenchymal tumors with blurred boundaries, as in Figure 3, and this type of mesenchymal tumors is suitable for open surgery. During open surgery, the tumor boundary can be touched, and even the stomach wall or intestinal wall can be cut directly to see the tumor boundary, which can be more intuitive and accurate to remove the tumor, avoiding too much resection affecting the function of organs or not enough resection leading to residual tumor. The core of gastrointestinal mesenchymal tumor surgery, or the most critical issue, is to avoid intraoperative rupture. Because once the mesenchymal tumor ruptures intraoperatively, it is directly classified as very high-risk and very easy to recur. Therefore, extra care needs to be taken intraoperatively to avoid tumor rupture. For doctors who are experienced in treating mesenchymal tumors, it is relatively easy; however, for doctors who are inexperienced in treating mesenchymal tumors or have insufficient knowledge about mesenchymal tumors, especially those who are not gastrointestinal oncologists, it is indeed more difficult to achieve complete resection. In clinical practice, we often encounter patients with small intestinal mesenchymal tumors being operated as ovarian tumors without realizing that they are mesenchymal tumors, and intraoperative rupture is a common occurrence, which is very regrettable. So, what are the measures to avoid or minimize tumor rupture intraoperatively? Firstly, we should operate gently and try not to touch the tumor directly, if it is necessary to touch, it is better to cover it with gauze or gauze pad and try not to squeeze it; for tumor with large volume and cystic fluid or blood accumulation inside the tumor, try to cover the surrounding normal organ tissues with gauze or gauze pad around the operation area to prevent the cystic fluid from spreading in case of rupture; for tumor with special location or large volume or obvious adhesions, we should actively open the tumor to avoid rupture. For tumors with special location or large tumor size or obvious adhesions, active open surgery will be performed. The surgical incision should be larger than the largest diameter of tumor to avoid extrusion and rupture in the process of removal. It is better to put the specimen into the bag before taking the specimen, even if the rupture will not contaminate the abdominal cavity and abdominal wall wound. Lymph node dissection is not required routinely Gastrointestinal mesenchymal tumor rarely occurs lymph node metastasis, so it is not necessary to standardize regional lymph node dissection like gastric cancer or colorectal cancer surgery. However, if there are obviously enlarged lymph nodes around the tumor found intraoperatively, it is recommended to clear them, preferably by intraoperative freezing for clarification. However, resection of enlarged lymph nodes with pathologically confirmed metastases should be considered for patients with GIST with SDH defects. V. Surgical resection is flexible and does not require regular resection There is no fixed surgical pattern for gastrointestinal mesenchymal tumor surgery, regardless of whether the stomach, small intestine or colorectum is unnecessary to do regular resection, especially if the tumor is located in a special site. For example, the cardia, near the pylorus or distal rectum. The principle of resection is to make a conformal resection according to the specific location and size of the tumor, without adhering to a fixed surgical pattern, and to preserve the function of the organ where the tumor is located to the greatest extent while removing the tumor completely. For example, for tumors near the esophagogastric junction, the tumor can be removed by manual incision of the gastric wall under direct vision, and then the wound can be manually sutured to preserve the function of the cardia to the greatest extent; for tumors in the distal rectum, local excision should be performed at every opportunity to preserve the function of the anal sphincter, and if necessary, medication can be administered first, and then surgically removed after the tumor shrinks, Figure 4. After local excision, both the anal function and the radicality of tumor removal are very ideal, avoiding the combined abdominal perineal resection. For recurrent metastases or advanced gastrointestinal mesenchymal tumors at the initial diagnosis, surgery is generally not considered. Puncture biopsy is performed to clarify the pathology, and drug therapy, mainly oral imatinib treatment, is performed according to the results of genetic testing to control the disease progression. However, if the patient has intestinal obstruction or bleeding problems, palliative surgery may be considered to relieve symptoms. Post-operative drug maintenance therapy will be continued.