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Page 2 of 9 Genova et al. Mini-invasive Surg 2020;4:20 I http://dx.doi.org/10.20517/2574-1225.2019.47

[1,2]
upper rectum, which frequently appeared inaccessible . That often compromised the quality of surgical
[1,2]
resection , with a rate of positive margins higher than 10% even in the series of the most experienced
[3,4]
surgeons .
The attempt to overcome the limitations of TAE stimulated the development of transanal endoscopic
[5]
microsurgery (TEM). Introduced in the early 1980s by Buess et al. , this technique involved the use of three
main components: a specific rigid proctoscope, a dedicated camera, and modified laparoscopic instruments.
In particular, the rigid proctoscope was fixed to the operating table, oriented by the surgeon, and provided
with several ports for pneumorectum creation, smoke evacuation, the camera, and instruments. Operative
steps were quite similar to TAE, and the surgical wound resulting from full- or partial-thickness wall
resection could be left open or closed by several techniques (such as sutures or clips).

Compared to TAE, TEM allowed an easier resection of rectal tumors lying in the middle or upper rectum,
[6]
making excision possible even in some cases of lower sigmoid colon lesion . Moreover, several studies
showed better outcomes after TEM [3,7-10] . Notably, a systematic review with meta-analysis published by
[8]
Clancy et al. in 2015 reported significant differences in terms of negative resection margins, specimen
fragmentation, and local recurrence in favor of TEM, whereas the postoperative complication rate was
similar between conventional TEM and TAE.

However, TEM showed to have some important limitations. Notably, the dedicated surgical equipment was
designed for an up-to-down approach to rectal lumen. That made the resection of anterior rectal lesions
quite challenging, requiring to place the patient in a prone position and to use specific split-leg operating
tables. Moreover, the necessary surgical material was expensive and the learning curve long. Hence, the
[1,2]
implementation of TEM remained limited .

To provide an alternative to TEM for local excision of rectal tumors, in 2009, an American surgical team
[11]
from Florida introduced a new technique called transanal minimally invasive surgery (TAMIS) .

The present study is intended to provide a general overview on TAMIS, summarizing its most important
aspects and focusing on the association with robotic technology and its implementation.

TAMIS: TECHNICAL ASPECTS AND INDICATIONS
TAMIS is a surgical technique introduced by Atallah, Albert, and Larach in 2009 to provide an alternative to
[11]
TEM for local excision of rectal neoplasia .
It combines the use of a disposable multichannel port placed transanally with conventional laparoscopic
equipment. Notably, the pneumorectum is achieved using common laparoscopic systems inflating CO , and
2
[1]
the endoluminal pressure ranges between 15 and 25 mmHg . A 30°- or 45°-angled 5-mm laparoscope is
preferable [12,13] , whereas conventional laparoscopic instruments are used for manipulation. Initially, single-
site multichannel ports conceived for laparoscopic abdominal surgery were adapted to a transanal use. Later,
several devices were specifically designed [12-14] .

TAMIS is indicated for the local excision of a number of benign and premalignant tumors of the rectum
located at up to 15 cm from the anal verge [15-19] . This technique may also represent a curative treatment for
selected patients with rectal cancer. Notably, according to the National Comprehensive Cancer Network
[20]
guidelines 2018 , transanal local excision may be an appropriate therapeutic option in case of early-stage
T1 tumors with small size (< 3 cm), well to moderate differentiation, location within 8 cm from the anal
verge, and extension to less than 30% of rectal circumference. The resection must be full-thickness and
assure more than 3-mm negative margins. The specimen must be oriented and pinned before fixation. In the