Gastrointestinal mesenchymal tumor (GIST) is a rare tumor occurring in the gastrointestinal tract, which was firstly introduced by Mazur et al. in 1983.GIST is a type of mesenchymal tumor with specific histological, immunophenotypic and molecular genetic characteristics.The incidence of GIST is extremely low, and rectal mesenchymal tumor is even rarer. In this study, we retrospectively analyzed the clinical data of 7 patients with rectal mesenchymal tumor treated at the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine from January 2002 to October 2007, and discussed the clinical diagnosis and treatment of rectal mesenchymal tumor by combining relevant literature. Data and methods 1. General data Seven patients with rectal mesenchymal tumor were operated patients between January 2002 and October 2007, and all cases were confirmed by pathology after surgical resection of large specimens. Among them, 5 cases were male and 2 cases were female, aged 44-67 years. The first symptoms were blood in the stool or anal swelling and increased frequency of stool. The tumors were all located in the middle and lower rectum, including 5 cases of intramural type and 2 cases of extramural type. All patients in this group received anorectal examination, fiberoptic colonoscopy and MRI examination before surgery, and none of them had a clear diagnosis before surgery. The preoperative tumor markers such as CA199, CEA, CA125 and AFP were in the normal range. 2. Methods All 7 patients underwent surgical treatment, 2 cases were surgically resected via sacrococcygeal approach, 3 cases were locally resected via anus, 2 cases were combined abdominoperineal resection (1 of them was recurred after local resection 18 months ago). 2 cases were extra-mural resected via sacrococcygeal approach, 1 tumor was located in the right anterior rectum, about 3.0×4.0 cm in size, 1 tumor was located in the posterior interstitial space of pre-sacral rectum (the upper edge of tumor was flat in sacral 4 plane) Among the five cases of intramural type, three tumors were located in the middle and lower rectum, with the size of 0.4×0.5cm, 2.0×3.0cm and 3.0×3.0cm respectively, and the tumors were located in the submucosal layer of the rectum (not involving the muscular layer), and were excised locally through the anus. The tumors were located in the submucosal layer of the rectum (not involving the muscular layer), and local resection was performed through the anus, and in one case, part of the rectal muscular layer was resected at the base, and intraoperative rapid frozen pathological examination did not show any residual tumor. The results 1, all patients in this group were discharged with one stage of healing. 7 cases were found to be spindle cells under light microscopy and pathologically confirmed as rectal mesenchymal tumor, see Figure 1. 5 of them were examined by immunohistochemistry and the results were: 5 cases were positive for CD117, 5 cases were positive for CD34, 4 cases were positive for anti-smooth muscle antibody (SMA), 2 cases were positive for P53, acidic calcium binding protein (S The patients were negative for acidic calcium binding protein (S-100) and nodulin (Desmin). 2. Follow-up results Follow-up was by telephone and regular review at outpatient clinics. Among the 7 cases in this group, 6 cases were completely followed up, 1 case was lost, and the follow-up time was 1~40 months. 1 case was followed up for 1 month after surgery, 2 cases were followed up for 5 months after surgery, 1 case was followed up for 13 months after surgery, 1 case was followed up for 19 months after surgery, and no recurrence was seen; 1 case was recurred in 18 months after local excision through the anus, and then combined abdominal perineal excision was performed, and died in 22 months after surgery due to local recurrence. Discussion 1. Incidence of rectal mesenchymal tumor: GIST is a rare tumor occurring in the gastrointestinal tract, which is a mesenchymal tumor with a very low incidence, accounting for 1% of all gastrointestinal tumors, of which rectal mesenchymal tumor accounts for about 5%. Rectal mesenchymal tumor is common in middle-aged and elderly patients, age can occur from 27 to 70 years old, and it is more common in men. 2. Clinical diagnosis of rectal mesenchymal tumor: common clinical symptoms of rectal mesenchymal tumor include blood in stool, anal swelling, increased number of bowel movements, anorectal pain and obstruction. The occurrence of clinical symptoms is related to the size of the tumor. Those with small size are often asymptomatic and only found by physical examination or unintentionally. If the tumor is large, forward pressure on urethra may cause difficulty in urination and frequent urination, and backward pressure on rectum may cause difficulty in defecation. Nearly 90% of rectal mesenchymal tumors are <7cm from the anal verge, so anorectal palpation is the simplest and most effective means, which can palpate submucosal or extra-mural rectal masses, mostly clear, smooth and tough or hard. Fiberoptic colonoscopy can exclude ectopic intestinal tumors, and sometimes endoscopy cannot observe the actual tumor. Preoperative intracavitary ultrasound and MRI or CT examination should be performed. When we do pelvic MRI, water bladder is usually injected into the rectum for contrast to make the rectum filled, which can clearly observe the location, size and relationship between tumor and surrounding tissues and organs, and help to judge the possibility of tumor surgical resection before operation. If internal bleeding and necrosis of tumor or destruction of tumor capsule wall are seen, and unclear demarcation between tumor and surrounding organs, it often indicates increased invasiveness of tumor [1]. Transanal proctoscopy or endoscopic ultrasound-guided puncture to obtain tissue E staining and CD117 staining is the best method for preoperative diagnosis. 3. Pathological diagnosis of rectal mesenchymal tumor: Because tumors are mostly located in the submucosa of rectum, it is very difficult to obtain biopsies, so it is difficult to make a clear diagnosis before surgery, and pathological examination after surgical resection is required to make a clear diagnosis. Pathological diagnosis is based on specific histological manifestations and immunohistochemical examination, both of which are indispensable. The cell morphology of rectal mesenchymal tumors is divided into spindle cell type, epithelioid cell type and mixed type, and spindle cell type is the most common, accounting for more than 90%. The most diagnostic value of immunohistochemical testing is positive CD117 expression [2], and the positive rate of CD117 in GIST is as high as 85-100%, and positive CD34 expression is very useful for diagnosis. In our five cases, immunohistochemistry CD117 and CD34 were positively expressed. 4. Treatment of rectal mesenchymal tumor: surgical resection is the only treatment that has the potential to heal patients with rectal mesenchymal tumor [3]. The choice of surgical method and the scope of surgical resection mainly depend on the size of the tumor, the location of the tumor, the distance of the tumor from the anal verge and the pathological results of preoperative puncture. For tumors with diameter ≤2 cm, "benign" mesenchymal tumors are generally considered and local excision is feasible; for tumors with diameter ≥5 cm, the recurrence rate after local excision is high and radical excision is recommended; for tumors with diameter between 2 and 5 cm, specific analysis should be made, and local extended excision is feasible for low tumors considering postoperative quality of life, but regular review is necessary. For high tumor, radical anterior rectal resection is recommended. During surgery, complete resection of the tumor and extensive surrounding normal tissues should be performed to avoid rupture of the tumor, especially the principle of tumor-free in the first surgery is most important to prevent recurrence after surgery. According to Hassan et al [4], tumor <2.5 cm, confined to the intestinal wall, local extended resection (LAR) is feasible. The recurrence rate of combined abdominoperineal resection (APR) for rectal mesenchymal tumors is low, about 20%, and the results are better than local resection. changchien et al [5] believed that APR and LAR can reduce the recurrence rate, but not reduce metastasis and improve survival. For patients with recurrence and large tumor size, invasion of adjacent organs without distant metastasis, combined organ resection is feasible to improve the prognosis. After the appearance of liver metastasis, if the tumor is confined to one lobe or the number is small, surgical resection can be considered. For multiple or large metastases that cannot be resected, hepatic artery cannulation embolization is feasible. Traditional chemotherapy and radiotherapy have little effect on rectal mesenchymal tumor. In recent years, as molecularly targeted drugs have entered the oncology clinic, imatinib myselate (Glivec, Glivec), a tyrosine kinase receptor inhibitor, has achieved promising clinical efficacy in the treatment of GIST. Preoperative use of Glivec resulted in symptom relief, tumor shrinkage, and improved rates of complete tumor resection [3]. 5. Prognosis of rectal mesenchymal tumor: The literature reports that the 5-year survival rate of those with complete resection of gastrointestinal mesenchymal tumor is 54%. The recurrence rate of rectal mesenchymal tumor after resection is very high, up to 40%~80%, which may be related to the rupture of tumor envelope caused by the extrusion of tumor during resection, resulting in implantation. Since rectal mesenchymal tumors are not clinically common, there are few reports of large samples in the literature, and long-term accumulation and multicenter follow-up studies of bulk data are needed for clinical treatment.