I. DISEASE OVERVIEW GIST is a unique and relatively rare tumor, currently defined as a c-kit-positive mesenchymal (interstitial or connective tissue) tumor that occurs in the gastrointestinal tract and has specific histologic features. Histologically, GISTs are classified as benign or malignant, and most are diagnosed as benign; however, clinicians and pathologists currently believe that all GISTs contain more or less malignant potential. Epidemiology The age of onset of GIST is usually 50-70 years (median age 55-65 years), with rare onset before 40 years of age. The current estimated incidence is approximately 10-20/100,000 with no gender, racial or geographic differences. However, recent developments in the study of this disease suggest that the incidence of GIST may be much higher than currently estimated. The majority of GISTs originating in the mesenchymal tissue of the gastrointestinal tract account for approximately 1% of gastrointestinal tumors. Most GISTs (60-70%) occur in the stomach, 20-30% in the small intestine, 5% in the colon and rectum, and <5% in the esophagus, while a few GISTs can also occur in other sites, such as the omentum and mesentery, and about 20-30% are malignant when detected.The exact pathogenesis of GISTs is not known. Histopathology Tumors of mesenchymal origin in the gastrointestinal tract exhibit a typical spindle cell morphology and are often classified as smooth muscle cell tumors (e.g., smooth muscle tumors, or smooth muscle sarcomas) or tumors originating in neural tissue (e.g., Schwann's cell tumors, neurofibromas). Although the GIST phenotype varies greatly, morphologically, approximately 80% are spindle-shaped while 20% are epithelioid, and very few are malignant. Clinical manifestations Depending on the location of the tumor, the type of growth and the size of the tumor, the manifestations of GIST are different, and GIST can range from a few millimeters to more than 40 centimeters. ① 50-70% of patients have abdominal mass that may be palpable, which is the most common symptom, and may be accompanied by vague abdominal pain and discomfort. ② Gastrointestinal bleeding, which occurs in about 1/3 of patients. ③ Less common nonspecific signs and symptoms include anorexia, weight loss, nausea, gastrointestinal obstruction, or obstructive jaundice. ④ Many small tumors can be asymptomatic and are often found unintentionally during surgery or other tests. ⑤ GISTs can occur anywhere in the gastrointestinal tract. The stomach and small intestine are the most common primary sites, accounting for 60-70% and 20-30% of cases, respectively, while other GISTs may occur in the esophagus, omentum, mesentery, colon, and rectum.Metastasis of GISTs initially occurs in the abdominal cavity and often spreads to the liver, less frequently involving the lymph nodes. V. TREATMENT Prior to 2001, surgery was the only effective treatment for GIST, and only complete resection of the tumor could result in a cure. However, the incidence of intra-abdominal local recurrence is quite high even for patients with complete resection of the tumor and no tumor seen microscopically. Because of the poor efficacy of chemotherapy for metastatic GIST and the lack of sizable studies of postoperative systemic chemotherapy, postoperative adjuvant chemotherapy is generally not recommended except in pilot studies. Radiotherapy is less commonly used in GIST because tumors are highly resistant to radiation and their surrounding organs are more sensitive to radiation. Even though the efficiency of chemotherapy is low, most patients with metastatic and/or unresectable GIST receive multiple courses of chemotherapy due to the absence of other more effective treatments. Different chemotherapy regimens including multi-agent combinations of chemotherapy, such as adriamycin, alpha-interferon, and cetamidopiperidone are used to treat residual tumors, but with little efficacy. However, Gleevec, a specific inhibitor of c-kit receptor tyrosine kinase, has largely improved the prognosis of patients with malignant GIST. The clinically recommended dose of Gleevec is 400mg/day, and if satisfactory results are not obtained and there are no adverse effects, the dose can be increased to 600mg/day for a period of 6-12 months. Prognosis: It is often difficult to predict the clinical behavior of GISTs, and because most pathologists believe that GISTs are not truly benign, the term "benign" as opposed to "malignant" has been replaced by "high risk" as opposed to "high risk". The term "benign" as opposed to "malignant" has been replaced by "low risk" and "non-deterministic malignant potential" as opposed to "high risk". Introduction to Gleevec 1. Mechanism of action: Gleevec (tyrosine kinase inhibitor) is a derivative of 2-phenylaminopyrimidine. It selectively inhibits a few related tyrosine kinases, including C-KIT, bcr-abl and platelet-derived growth factor receptors. Gleevec binds to the ATP-binding site in the cytosolic{intracellular tyrosine kinase functional region of C-KIT, blocking the transfer of the phosphate group from ATP to tyrosine residues of the protein substrate. This selectivity for C-KIT present in malignant GIST can lead to inhibition of cell proliferation and restoration of apoptosis. Thus the mechanism of action of Gleevec emphasizes the necessity of determining whether CD177 is present or not, and is an important part of selecting the best therapeutic regimen for the patient. 2.Main indications: (1) For the treatment of patients in the acute phase of lentigo, accelerated phase or chronic phase who have failed alpha-interferon therapy. (2) For the treatment of adult patients with unresectable and/or metastatic GIST. 3, Adverse reactions: (1) Most common: nausea, vomiting, diarrhea, malaise, myalgia, myalgias, erythema, conjunctivitis. (2) Edema and water retention. Mostly periorbital and lower extremity edema, but chest and abdominal water and rapid weight gain have also been reported. (3) Pancytopenia and anemia. (4) Bleeding is less common (about 12-20%) 4. Precautions (1) Due to the occurrence of severe water retention, regular weight monitoring is recommended, and symptomatic treatment should be given if there is rapid weight gain. (2) Use with caution in patients with heart failure to avoid aggravation (3) In clinical trials, gastrointestinal bleeding occurred in 5.4% of patients and intra-tumoral hemorrhage in 2.7% of patients, so patients should be monitored for gastrointestinal symptoms during the dosing phase. (4) Use with caution in patients with hepatic or renal insufficiency. (5) It is advisable to check the whole blood image once a week in the first month of Gleevec treatment and once every two weeks in the second month. Later on, as needed (e.g., every 2-3 months), liver and kidney function should be monitored before drug administration, and then once a month, if necessary.