**2.2 Mucosal layers of rectal wall**

Another anatomical landmark is differentiating the mucosal layers (**Figure 4**) in relation to the TNM classification of the rectal cancer.

**Figure 4.** *Mucosal layers of rectal wall (axial T2 weigted MR image).*

T1- submucosal invasion.

T2- invasion of muscularis propria.

T3- through the muscularis propria to the submucosa.

T4- perforation of the visceral peritoneum or direct invasion of the peritoneum.

Important fact is that T3 and T4 tumors are associated with extramural invasion. The more pronounced penetration of the mesorectum is associated with a worse prognosis and a higher probability of local recurrence. Many tumors are staged as pT3, but there is actually a heterogeneous T3 group, which is why a subclassification of T3 has been created:

T3a - minimal invasion <1 mm by muscularis propria.

T3b- light-walled invasion 1-5 mm from muscularis propria.

T3c- moderate invasion 5-15 mm from muscularis propria.

T3d- extensive invasion>15 mm by muscularis propria.

T3a and T3b are associated with better outcome for the patient compared with T3c and T3d stages, suggested they are T4 tumors because of worse outcome and poor prognosis [1].

When talking about staging it is important to notice that low rectal cancer is a separate subgroup again due to different anatomical features- the anorectal sling:

Staging of low rectal cancer with MRI (recently validated in the prospective study Mercury II: Low Rectal Cancer study [2].

stage 1 - the tumor is visualized in the rectal wall, but not throughout its thickness (preserved outer muscle layer).

stage 2- the tumor displaces the muscle layer without crossing the intersphincteric line.

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*Role of Magnetic Resonance Imaging in Patients with Rectal Cancer*

stage 3- the tumor invades the intersphincteric line or is 1 mm from the

For understanding of the neoplastic behavior of rectal cancer it is of great importance to analyze the pathways of spreading of tumorous tissue. They are:

2.involvement of local lymph vessels and lymph node metastases,

3.venous invasion (intra- and extramural venous invasion- EMVI) and

Demonstration of any invasion both histologically and by MRI [3] is always associated with a poor prognosis. The detection of EMVI is associated with the presence of synchronous distant metastases. Involvement of extramural venous vessels is more closely associated with poor prognosis, as well as invasion of larger veins. This leads to the conclusion, that detection of EMVI on MRI is of great prognostic

Explaining the anatomy by the radiologists helps the surgeons plan the surgical

2.TME- Total Mesorectal Excision is the universally established standard for optimal oncological surgery in rectal cancer [4]. TME is an independent predictor of local recurrence. TME includes excision of the rectum and surrounding adipose tissue, the lymphovascular cuff, the mesorectum, in which the locoregional lymph nodes are located. The outermost border of the mesorectum, the mesorectal fascia, plays the role of an oncological barrier. Thus, if the surgical principles for TME are followed, the prognostic effect of regional lymph nodes

may be neglected [5], as they themselves are removed en block in TME.

4.No surgery and stoma placement in locally advanced and unresectable T4b

Before discussing the imaging of rectal cancer one should understand the treatment options for the disease. The ideal prognostic stage allows selection of the

3.Deferral of surgery or Watch and Wait strategy- novel strategy based on organ preservation if complete clinical response is achieved by neoadjuvant therapy (references on EURECCA (European Registration of Cancer Care [6] and

stage 4- the tumor invades the external anal sphincter and infiltrates the levator

*DOI: http://dx.doi.org/10.5772/intechopen.94868*

ani and/or invades neighboring organs.

1.direct invasion in the rectal wall,

importance and it is explained in details below.

1.TEM- Transanal Endoscopic Microsurgery in T1 stage

**2.3 Pathways of spreading**

4.tumor deposits.

**2.4 Surgery of rectal cancer**

TRIGGER) [7].

tumors.

**2.5 Treatment options**

procedure. Surgeons have 3 options:

levator ani.

stage 3- the tumor invades the intersphincteric line or is 1 mm from the levator ani.

stage 4- the tumor invades the external anal sphincter and infiltrates the levator ani and/or invades neighboring organs.
