0:01

So before we do that, the next thing after we look at

0:04

the nodal staging from an AJCC classification is to

0:09

kind of get a sense of what constitutes regional lymph

0:12

nodes and what constitutes non-regional lymph nodes.

0:14

So any lymph nodes that are present within the outline

0:18

of the mesorectal fascia, and these are referred to

0:21

as mesorectal lymph nodes, are clearly regional nodes.

0:26

These nodes will extend superiorly along

0:30

the branches of the IMA, and they can go all

0:33

the way up to the origin of the inferior mesenteric

0:37

vessels; those are all still regional lymph nodes.

0:41

Now, there is another class of regional nodes that we

0:44

need to pay attention to and also be extra vigilant

0:48

in terms of identifying, and the two anatomic areas

0:50

that are considered regional are internal iliac

0:53

nodes, which are outside the mesorectal fascia.

0:56

So these are referred to as extra

0:58

mesorectal regional lymph nodes.

1:00

And so the first one is in the vicinity

1:02

of the internal iliac chain.

1:06

And the second is along the obturator internus

1:09

muscle, which we refer to as the obturator chain.

1:12

And so how do you know what is internal iliac and

1:15

what is obturator? What you do is you draw a line

1:18

through the pudendal or the internal iliac artery.

1:22

Whatever is medial to this line is

1:24

internal iliac node, and whatever is lateral

1:27

to this line is an obturator lymph node.

1:30

So those are also considered regional.

1:32

So remember it's mesorectal and internal iliac.

1:37

Those are all considered regional.

1:40

This is mesorectal.

1:41

These are extra mesorectal, pelvic

1:43

sidewall, regional lymph nodes.

1:45

If you have external iliac lymphadenopathy, which is

1:48

along the external iliac vessels, anteriorly or medially,

1:51

those are considered to be distant metastases.

1:55

They are not regional lymph nodes.

1:59

One other important point is, and again,

2:02

this is a point of debate, is if you

2:04

have a rectal cancer that extends into the anal

2:07

canal below the level of the dentate line, in those

2:10

patients, you can get inguinal adenopathy.

2:14

If you ask a radiation oncologist, they will

2:17

consider inguinal nodes for low-lying rectal cancer

2:20

that extends below the level of the dentate line

2:23

as regional nodes and they will typically

2:25

include that in the radiation field when

2:26

they do neoadjuvant chemoradiation therapy.

2:29

So that's sort of the anatomic distribution of what is

2:33

regional in the mesorectum, what is extra mesorectal

2:36

regional, and what are non-regional lymph nodes.