TEM (Transanal Endoscopic Microsurgery) is a minimally invasive anus-preserving surgical method for the removal of tumors through the anus, developed by German physicians Buess and Mentges in 1980-1983 and first used in clinical practice in 1983. Medical Instruments Corporation, Knittling, Germany), combining a high-quality visual system and a pressure-regulated insufflation device, the proctoscope has a diameter of 4 cm and an axis length of 12 cm and 20 cm to accommodate lesions of different sites, and is fixed to the operating table by a fixation device with a proctoscope panel with four A special endoscopic device including tissue grasping forceps, scissors, straight and curved needle-tipped electrocoagulators, etc., is used to perform surgical operations through the operating holes, and another channel is available for stereoscopic use and can be connected to the image monitoring system. Compared with the traditional transanal surgery, TEM can reach the middle and upper rectum, the rectum and the lesion are clearly exposed after magnification and inflation, the tissue structure is accurately identified, the instrumentation is unobstructed, the needle-like electric knife can perform precise bloodless separation and tumor resection, the cut edge is well exposed, the hemostatic suture of the rectal wall is precise, and the narrowing of the intestinal lumen caused by overlapping sutures can be avoided. Another advantage is the complete resection of the mass without fragmentation, which avoids tumor contamination and is more conducive to accurate pathological analysis, which is helpful for further surgical or radiological treatment decisions. tEM avoids complications and abdominal wounds caused by major surgery, is painless after surgery, has no restriction of activity, has a rapid recovery, and has significantly less operative time, bleeding, postoperative analgesia, and average hospital stay than transabdominal surgery. Operation of TEM Endoluminal ultrasound and proctoscopic examination are required before TEM operation. Endoluminal ultrasound is performed to determine the depth and stage of the tumor, and proctoscopy is performed to determine the distance of the tumor from the anal verge and the position of the tumor in the rectum (anterior, lateral or posterior wall) to determine the surgical position (prone folding position, lateral position or lithotomy position), with the principle that the tumor is located below the field of view. Bowel preparation and prophylaxis with antibiotics are the same as for general bowel surgery. TEM can be performed under general or local anesthesia, starting with a 1:100,000 epinephrine injection around the submucosa of the lesion to augment the mucosa and reduce bleeding. The operation is performed with a needle electric knife. small adenomas and benign lesions are excised to the submucosal layer with a 0.5 cm margin. large adenomas or carcinomas require total rectal wall excision, except to the perirectal fat, with a 1 cm margin. rectal wall defects are closed with 2-0 Viejo or PDS sutures in one continuous stage without knots and fixed with a special silver clip. The surgical specimen was stapled on hardboard paper for the pathologist to mark the orientation and lateral margins for more accurate pathologic analysis. Indications for TEM Non-tipped, broad-based benign rectal adenomas with a maximum diameter of more than 1.5 cm (stage T0), especially villous adenomas, are most suitable for TEM treatment. The design of the special instrumentation of TEM allows the removal of rectal tumors located at any distance between 5 and 20 cm from the anal verge. For rectal carcinoma in situ (Tis stage) or T1 stage rectal carcinoma with low risk of recurrence (e.g., highly or moderately differentiated tumor, small tumor size, high mobility), TEM offers a high chance of cure. Although, rectal cancers with high risk of recurrence at stage T1 or more advanced (e.g., stage T2 or above) have a high chance of recurrence after local resection, TEM still provides an ideal palliative treatment for those patients with high surgical risk, such as those of advanced age or with severe comorbidities. Other indications for TEM: rectal carcinoid tumors, mesenchymal tumors, rectal strictures and even rectovaginal fistulas are ongoing clinical trials of TEM combined with adjuvant radiotherapy for pT2 rectal cancer. Contraindications to TEM: TEM is contraindicated for stage T1 rectal cancer with high risk of recurrence or more advanced (e.g., stage T2 or higher) rectal cancer if not for palliative treatment; simultaneous multiple primary colorectal tumors are contraindications to TEM and should be ruled out by preoperative total colonoscopy, barium enema angiography, or multi-row CT colorectal reconstruction. TEM may affect the anal sphincter to a certain extent because a special rectoscope with an external diameter of 4 cm must be inserted through the anus until the end of the operation. Therefore, TEM should not be performed in patients with poor anal sphincter function to avoid postoperative anal incontinence. Superiority of TEM: TEM provides a safe and effective method of treating benign rectal adenomas and early rectal cancer. This minimally invasive surgical approach combines the advantages of endoscopic, laparoscopic and microsurgery, has a lower complication rate and shorter postoperative hospital stay, and minimizes the need for an enterostomy.