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case of negative pathological features, such as positive resection margins, lymphatic and vascular invasion,
poor differentiation, or Kikuchi sm3 level, a more radical resection is needed. Moreover, TAMIS could also
be indicated in the case of more advanced T-stage rectal cancer in order to provide an excisional biopsy
for a more precise pathologic examination or to treat patients at high surgical risk in association with other
treatments [13,14] .

The principles of local resection are similar in TEM and TAMIS. First, the lesion must be marked around its
circumference. Benign tumors may be excised limiting the dissection to the submucosal layer, without need
[13]
to close the surgical wounds . On the contrary, malignant tumors require a full-thickness resection of the
[13]
rectal wall . Moreover, in the case of posterior tumors, a small amount of perirectal fat may be excised en
[13]
bloc to ensure a complete excision and allow lymph node analysis .
When rectal tumors are located posteriorly, it would not be necessary to close a full-thickness defect because
of its extraperitoneal position, as suggested by several authors reporting no higher complication rate after
leaving surgical wounds open [13,21] . However, this time-consuming practice is recommended to cover an
eventual peritoneal entry [13,22] . In particular, the wall defect is generally closed transversely, using separated or
running sutures, clips, or other devices [1,13] . Peritoneal entry represents a well-known complication of TAMIS
[12]
and it is described more frequently when tumors are located anteriorly in the middle or upper rectum .
[12]
When it occurs (1% of cases ), it is recommended to use a steep Trendelenburg position to facilitate wall
repair and to convert to laparoscopy if it is impossible to maintain an adequate pneumorectum [22-24] . With
this regard, some authors suggest placing the patients in a prone position to limit the amount of CO passing
2
[25]
into the peritoneal cavity . Among the postoperative complications of TAMIS, a rectovaginal fistula can
[12]
also occur, besides common general surgery complications, such as bleeding (2.8%) , fever, urinary tract
infections, and atrial fibrillation.

TAMIS: OUTCOMES
[12]
In 2014, Martin-Perez et al. published a systematic review of the literature about TAMIS, including 24
retrospective studies and 9 case reports. The authors reported that up to eight alternative abbreviations
were used to indicate the same technique, and included overall 390 patients, undergoing TAMIS for
malignant lesions in 209 cases (53.5%), adenomas and high-grade dysplasia in 152 cases (39%), and
other pathology in 29 cases (7.5%). Among these latter 29 cases, 23 patients (79.3%) were operated
for neuroendocrine lesions, 3 patients (10.3%) for fibrosis, 1 patient (3%) for GIST, 1 patient (3%) for
mucocele, and 1 patient (3%) for melanoma. Surgical procedures were performed using eight different
TAMIS platforms, among which SILS port was the most commonly used (66.7% of all studies included).
The mean size of resected lesions was 3.1 cm (range: 0.8-4.7 cm), whereas the mean distance from the anal
verge was 7.6 cm (range: 3-15 cm). The authors reported only full-thickness excisions in 22 studies (60.6%),
only partial thickness excisions in 3 studies, both full-thickness and partial thickness excisions in 8 studies
(24.2%), and no precision about the extent of resection in 5 studies (15.2%). Conversion rate to TAE,
TEM, or abdominal laparoscopic surgery was 2.31% (9/390). The mean operative time was 76 min (range
25-162 min), the complication rate was 7.4%, and the mean hospital stay was two days. Considering the
publications reporting specific information about surgical resection quality, the rates of positive resection
margins, specimen fragmentation, and recurrence were 4.36% (12/275), 4.1% (4/97), and 2.7% (7/259),
respectively.

TAMIS VS. TEM
In the literature, several studies compared the outcomes of TAMIS and TEM [26-28] . Among them, it is
[28]
important to consider the large multi-institutional matched prospective study published by Lee et al.
in 2017. It included 181 patients undergoing TAMIS and 247 patients undergoing TEM, and showed that