TEM is a minimally invasive anus-preserving surgical method for the removal of tumors through the anus, developed by German doctors Buess and Mentges from 1980 to 1983 and first used in clinical practice in 1983. TEM is performed through a specially designed proctoscope that combines a high-quality visual system with 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 different lesions. A variety of special endoscopic devices, including tissue grasping forceps, scissors, straight and curved needle-tipped electrocoagulators, etc., are used to perform surgical operations through the operating holes; an additional channel is provided 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 rectal area, the rectum and 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 will determine the depth and stage of the tumor, and proctoscopy will determine the distance of the tumor from the anal verge and the position of the tumor in the rectum (anterior wall, lateral wall or posterior wall) to determine the surgical position (prone folding position, lateral position or lithotomy position), with the principle that the tumor will be 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 electrodebrider. small adenomas and benign lesions are cut to the submucosal layer with a 0.5 cm margin. large adenomas or carcinomas require total rectal wall resection, 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 (T0 stage), 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 cancer in situ (Tis stage) or T1 stage rectal cancer with low risk of recurrence (e.g., tumor is highly or moderately differentiated, small and mobile), 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 that is 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. If the tumor of the anterior rectal wall above the peritoneal reflex is resected by TEM, it is easy to cut through into the abdominal cavity, and although immediate intracavitary continuous suturing may be successful, TEM total resection for such cases must still be done with great caution. TEM requires insertion of a special rectoscope with an external diameter of 4 cm through the anus until the end of the procedure, which may affect the anal sphincter to some extent. 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.