History Gastrointestinal mesenchymal stromal tumor (GIST) is similar to smooth muscle tumor under microscope, and was often diagnosed as smooth muscle tumor or smooth muscle sarcoma in the past.In the 1970s, electron microscope and the 1980s immunohistochemistry technology were introduced, and GIST was further understood.In 1983, Mazur and Clark, a pathologist from the State University of New York in the United States, firstly proposed the concept of GIST. Clinical features Clinical features GIST belongs to mesenchymal tumors of the digestive tract, and most of them are positive for CD117 immunohistochemical staining. It can occur in all age groups, with a peak age of 50-70 years. The younger the age of onset, the higher the possibility of malignancy. It can occur in both sexes. The order of incidence in the gastrointestinal tract is stomach > jejunum > ileum > duodenum > rectum > colon. Symptoms of GIST are related to the location, size and growth pattern of the tumor. The most common symptom is abdominal pain and discomfort, which may also manifest as ulcers or bloody stools. Other rare symptoms include dyspepsia, loss of appetite, weight loss, nausea, and intestinal obstruction. Some patients may not have any symptoms. It can also be detected occasionally on physical examination without any signs or symptoms. GIST in the low rectum can be palpated by anal examination. Etiology c-kit is a proto-oncogene. In GIST, the c-kit gene undergoes a functionally acquired mutation and expresses a specific CD117/KIT antibody (c-kit proto-oncogene-associated protein) on immunohistochemistry. The failure of the anti-apoptotic mechanism of the cell after the mutation contributes to the rapid growth of tumor cells. Mutations in the c-kit gene are undetectable in a small percentage of GIST. It has been found that PDGFR-α mutations are also an important etiologic factor in the development of GIST. Surgical indications for GIST For lesions that are limited and have a maximum diameter of ≥2 cm, complete resection should be performed surgically in principle. If it is difficult to completely resect the GlST, it can be resected after the tumor shrinks with neoadjuvant targeted therapy. For tumors with a maximum diameter of <2 cm, there is no complete consensus yet. Surgery may also be considered if the lesion is complicated by bleeding, obstruction, or perforation. The decision to perform adjuvant therapy is based on the post-resection risk grading. (See table below.) Post-excision risk grading of primary GIST Surgical principles Intraoperatively, the integrity of the tumor envelope should be ensured. Mesenchymal tumors are fragile, and tumor implantation and metastasis may occur after rupture, seriously affecting the prognosis. If the tumor invades adjacent tissues and organs, the tumor body should be resected in its entirety together with the invaded and adherent tissues and organs.Lymph node metastasis rarely occurs in GIST, and routine clearance is not necessary unless there are clear signs of lymph node metastasis. Rectal mesenchymal tumors are unique due to anatomic and physiologic aspects. Intraoperative stripping of rectal mesenchymal tumors is extensive and affects the nerves, leading to postoperative bowel and urinary difficulties. For smaller rectal mesenchymal tumors, local excision can be performed while ensuring R0 resection. With the introduction and use of targeted agents such as imatinib mesylate in recent years, according to the NCCN guidelines and ESMO guidelines, it is considered necessary to treat the tumor medically before performing surgery to preserve function whenever function may be affected.