1. What is gastrointestinal mesenchymal tumor and what is the difference between it and smooth muscle sarcoma? A: Traditionally, almost all mesenchymal-derived tumors occurring in the gastrointestinal tract are classified as smooth muscle tumors, including smooth muscle tumors, smooth muscle sarcomas and their various subtypes, but recent studies have shown that most mesenchymal-derived tumors in the gastrointestinal tract are different from typical smooth muscle tumors, but are a group of tumors with unique pathological features, called gastrointestinal mesenchymal tumors, or GIST for short. Marker studies have shown that the majority of tumor cells in GIST do not express smooth muscle tumor-specific markers, such as smooth muscle actin (-SMA) and muscle-specific antigen (MSA), and electron microscopic examination has also shown that tumor cells in GIST do not have the characteristics of smooth muscle cell differentiation. The most characteristic immunohistochemical markers of GIST are CD117 and CD34, the products of the c-kit gene, both of which are negative for smooth muscle tumors, and therefore CD117 and CD34 are essential for the differential diagnosis. CD117 and CD34 are important for the differential diagnosis of both. GIST tumors are usually asymptomatic when they are small, but when they are large, they may present with epigastric distension and discomfort, abdominal mass, and may be accompanied by blood in the stool. The age of patients is mostly between 30-70 years old, with an average of 54 years old. Both men and women can develop the disease. It occurs in the stomach, small intestine, rectum, and extremely rarely in the esophagus and colon. It occurs in about 5% of cases outside the gastrointestinal tract, such as the abdominal cavity, mesentery or retroperitoneum, and other organs. The biological behavior of GIST can range from benign → junctional → significantly malignant, often lacking clear histological boundaries. Studies have shown that some of the following parameters are suggestive of malignant GIST: 1) the diameter of the tumor exceeds 5 cm; 2) the tumor is ill-defined and invades the surrounding tissue; 3) tumor necrosis is visible; 4) nuclear division count > 10/50 high magnification field of light microscopy; 5) the cells are dense and have a marked heterogeneity. It should be noted that any of the above parameters cannot be used as a separate indicator to determine the benignity or malignancy of the tumor, but must be combined, and if 3 or more of them are satisfied, it can be clearly malignant. The above indicators can be used as the basis for risk grading, and high risk requires postoperative adjuvant therapy. Benign and junctional GIST can mostly survive for a long time after surgical resection. The local recurrence rate of malignant GIST is 30% and the death rate can be as high as 41%. The most common site of metastasis is liver, followed by abdomen and lung. 2.What is the effect of Gleevec in the treatment of gastrointestinal mesenchymal tumor? For the treatment of gastrointestinal mesenchymal tumor, surgical resection is preferred for patients who can be surgically removed. After surgery, according to the pathology report, patients with high risk should take Gleevec for 3 years, or at least 1 year if economic conditions do not allow. Patients who cannot be surgically removed or who have recurrence after surgery should be considered for Gleevec treatment only after the pathology report is clearly diagnosed, kit, and PDGFR gene mutation detection. The specific treatment plan needs to be decided by the clinician. According to available data, Gleevec treatment for advanced gastrointestinal mesenchymal tumors can benefit 80% of patients and can significantly extend the survival time of patients with mesenchymal tumors. Safety of Imatinib Most adverse reactions are mild to moderate, mainly edema (fluid retention), gastrointestinal symptoms, muscle and bone pain, headache, rash, flushing, etc. Grade III-IV adverse reactions occur in about 21.1% of patients, with about 5% occurring in larger tumors with necrotic bleeding (in the gastrointestinal tract or abdominal cavity), edema mostly around the eyes, and in severe cases (<5% < font="">) in the Thoracic, abdominal and pericardial effusions and pulmonary edema can be relieved by stopping the drug and using diuretics. Gastrointestinal reactions include nausea, vomiting, abdominal pain, and diarrhea, none of which are severe. Hematologic toxicity thrombocytopenia and neutropenia are common. Liver function abnormalities, elevated ALT, and elevated bilirubin in 1% to 3% of cases may return to normal with dose reduction or discontinuation.