*2.6.4 Assessing EMVI: extramural venous/vascular invasion*

Extramural vascular invasion is defined as the presence of tumor cells in vessels outside the lamina muscularis propria (**Figure 9**, arrows).

Positive mrEMVI is associated with low survival rates. The 3-year survival in mrEMVI-positive patients was 35% compared to 74% in mrEMVI-negative patients. mrEMVI-positive patients have a fourfold increased risk of developing distant metastases.

The radiological characteristics of EMVI observed on MRI are described in detail -The veins around the rectum are recognized on the T2 sequence as serpiginous or curved linear structures; in the tubular structures considered to be blood vessels, in addition to changes in the contour, there is a weakening of the signal.

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**Figure 10.**

*Lymph nodes (arrowheads).*

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

tumor signal in the lumen) and the vessel boundary.

*EMVI- extramural venous/vascular invasion (T2 weighted MR images).*

*2.6.5 Assessing N- stage*

**Figure 9.**

A complete evaluation of mrEMVI should include the following: (entry into small veins may produce a nodular border); location of the tumor relative to the large vessels; vascular caliber (the tumor causes the vessels to dilate and amplify the

The N-stage is an important risk factor for local recurrence. The size of the lymph

node itself is not indicative, as 15–42% of patients with rectal cancer have small (<5 mm) mesorectal lymph nodes containing tumor cells (**Figure 10**, arrowheads).

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

**Figure 8.** *CRM- circumferential resection margin (axial T2 weighted MR images).*

**Figure 9.** *EMVI- extramural venous/vascular invasion (T2 weighted MR images).*

A complete evaluation of mrEMVI should include the following: (entry into small veins may produce a nodular border); location of the tumor relative to the large vessels; vascular caliber (the tumor causes the vessels to dilate and amplify the tumor signal in the lumen) and the vessel boundary.
