**1. Introduction**

Transanal endoscopic microsurgery (TEM) is a minimally invasive technique introduced in 1983 by Professor G. Buess [1]. By merging endoscopy with microsurgery [2], Buess developed this natural orifice instrumentation and technique to overcome the technical difficulties that are inherent in the management of low rectal tumors, avoiding an invasive surgical procedure such as low anterior resection but with disease-free margins, unlike traditional local excision techniques. Before the development of TEM, the available methods for the management of rectal tumors included abdominal invasive surgery, in the form of anterior or posterior approach,

and traditional transanal local excision techniques. In the anterior approach, the anatomic and technical difficulties restricted the surgeon; the posterior approaches were extremely radical with significant morbidity and mortality. These methods included the York Mason para-sacrococcygeal trans-sphinteric approach [3] for middle rectal tumors and the trans-coccygeal Kraske approach [4] for upper rectal lesions. Both the posterior techniques had high rates of complications: wound infection, fistulae, chronic pain, fecal incontinence, stenosis, high incidence of permanent stoma [5, 6]. Traditional transanal local excision techniques had several disadvantages such as poor exposure and lighting, with consequently increased risk of local recurrence. These techniques included the Parks transanal [7] approach and its variations according to Francillon [8] and Faivre [9]. In the Parks' procedure [7] after positioning of Parks' retractor, adrenaline submucosal injection was performed to raise the submucosa from the muscle plane, then two sutures were placed for traction, the mucosa was marked at about 1 cm from the tumor with diathermy, and it was excised following the muscle plane until complete tumor removal, with subsequent closure of the defect. According to the Francillon's technique [8], several stitches were positioned on healthy mucosa at about 1 cm from the tumor, and their traction acted like a "parachute," whereby the rectal wall harboring the tumor could be excised together with adjacent perirectal fat. Finally, in the Faivre technique [9], a flap of ano-rectal mucosa hosting the tumor was created and excised.

Buess, together with Richard Wolf Medical Instruments Division, developed a specific rectoscope and dedicated instrumentation to accomplish a revolutionary, highly technological, and new technique of rectal tumors excision by a transanal organ sparing minimally invasive approach but preserving oncological radicality, due to a magnified binocular 3D vision and excellent lighting [10].
